Bug 659788 - Add icons for Windows 7 jumplist taskbar items. r=Standard8
authorSiddharth Agarwal <sid.bugzilla@gmail.com>
Wed, 10 Aug 2011 19:02:14 +0530
changeset 8729 923b924c9422bddc54a3d8c08b765da58dddeedd
parent 8728 4cb88997f292f9cb49d10603d741703551d6e5c0
child 8730 3d7a6ee8b730a2113bcc0831269df922caff87c1
push id158
push userbugzilla@standard8.plus.com
push dateTue, 27 Sep 2011 19:18:14 +0000
treeherdercomm-beta@e47b99c61e4d [default view] [failures only]
perfherder[talos] [build metrics] [platform microbench] (compared to previous push)
reviewersStandard8
bugs659788
Bug 659788 - Add icons for Windows 7 jumplist taskbar items. r=Standard8 The patch does the following at build time: - extract the icons from the mail-toolbar-aero.png sprite sheet - add an icon header to each png to convert it into an ico - embed the icos in the EXE To do this it adds the MIT-licensed pypng library to the tree.
build/png2ico.py
build/pypng/exnumpy.py
build/pypng/iccp.py
build/pypng/mkiccp.py
build/pypng/pdsimgtopng
build/pypng/pipasgrey
build/pypng/pipcat
build/pypng/pipcolours
build/pypng/pipcomposite
build/pypng/pipdither
build/pypng/piprgb
build/pypng/pipscalez
build/pypng/pipstack
build/pypng/pipwindow
build/pypng/plan9topng.py
build/pypng/png.py
build/pypng/pngchunk
build/pypng/pnghist
build/pypng/pnglsch
build/pypng/texttopng
config/config.mk
mail/app/Makefile.in
mail/app/splash.rc
mail/components/wintaskbar/windowsJumpLists.js
mailnews/base/src/nsMessengerWinIntegration.cpp
suite/app/splash.rc
new file mode 100644
--- /dev/null
+++ b/build/png2ico.py
@@ -0,0 +1,115 @@
+#!/usr/bin/env python
+# ***** BEGIN LICENSE BLOCK *****
+# Version: MPL 1.1/GPL 2.0/LGPL 2.1
+#
+# The contents of this file are subject to the Mozilla Public License Version
+# 1.1 (the "License"); you may not use this file except in compliance with
+# the License. You may obtain a copy of the License at
+# http://www.mozilla.org/MPL/
+#
+# Software distributed under the License is distributed on an "AS IS" basis,
+# WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
+# for the specific language governing rights and limitations under the
+# License.
+#
+# The Original Code is mozilla.org code.
+#
+# The Initial Developer of the Original Code is
+# the Mozilla Foundation.
+# Portions created by the Initial Developer are Copyright (C) 2011
+# the Initial Developer. All Rights Reserved.
+#
+# Contributor(s):
+#   Siddharth Agarwal <sid.bugzilla@gmail.com>
+#
+# Alternatively, the contents of this file may be used under the terms of
+# either the GNU General Public License Version 2 or later (the "GPL"), or
+# the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
+# in which case the provisions of the GPL or the LGPL are applicable instead
+# of those above. If you wish to allow use of your version of this file only
+# under the terms of either the GPL or the LGPL, and not to allow others to
+# use your version of this file under the terms of the MPL, indicate your
+# decision by deleting the provisions above and replace them with the notice
+# and other provisions required by the GPL or the LGPL. If you do not delete
+# the provisions above, a recipient may use your version of this file under
+# the terms of any one of the MPL, the GPL or the LGPL.
+#
+# ***** END LICENSE BLOCK *****
+
+import png
+import sys
+import StringIO
+import struct
+import ctypes
+
+# ref: http://msdn.microsoft.com/en-us/library/ms997538
+class ICONDIR(ctypes.LittleEndianStructure):
+    _pack_ = 1
+    _fields_ = [("idReserved", ctypes.c_ushort),
+                ("idType", ctypes.c_ushort),
+                ("idCount", ctypes.c_ushort)]
+
+class ICONDIRENTRY(ctypes.LittleEndianStructure):
+    _pack_ = 1
+    _fields_ = [("bWidth", ctypes.c_byte),
+                ("bHeight", ctypes.c_byte),
+                ("bColorCount", ctypes.c_byte),
+                ("bReserved", ctypes.c_byte),
+                ("wPlanes", ctypes.c_ushort),
+                ("wBitCount", ctypes.c_ushort),
+                ("dwBytesInRes", ctypes.c_ulong),
+                ("dwImageOffset", ctypes.c_ulong)]
+
+# R, G, B, A, so 4 columns per pixel
+COLS_PP = 4
+
+def main(infile, left, top, size, outfile):
+    img = png.Reader(filename=infile)
+    pixels = list(img.asRGBA()[2])
+    # Take the subarray out. This is the ugliest but probably most efficient way
+    # to do it
+    outpixels = [[0] * (size * COLS_PP) for x in xrange(size)]
+    for row in xrange(size):
+        for col in xrange(size * COLS_PP):
+            outpixels[row][col] = pixels[top + row][left * COLS_PP + col]
+
+    # Set up a 32bpp RGBA PNG.
+    writer = png.Writer(size=(size, size), bitdepth=8, alpha=True)
+    # Write to a memory buffer
+    outpng = StringIO.StringIO()
+    writer.write(outpng, outpixels)
+    outpngbuf = outpng.getvalue()
+    outpng.close()
+
+    # Set up an icon header
+    icondir = ICONDIR()
+    icondir.idReserved = 0
+    # Icons are type 1
+    icondir.idType = 1
+    icondir.idCount = 1
+
+    iconentry = ICONDIRENTRY()
+    iconentry.bWidth = size
+    iconentry.bHeight = size
+    # Truecolor images have color count set to 0
+    iconentry.bColorCount = 0
+    iconentry.bReserved = 0
+    # PNGs have 1 color plane
+    iconentry.wPlanes = 1
+    # We're RGBA, so 32 bits per pixel
+    iconentry.wBitCount = 32
+    # Length of the buffer
+    iconentry.dwBytesInRes = len(outpngbuf)
+    # The data will be right after the icondir and iconentry
+    iconentry.dwImageOffset = ctypes.sizeof(icondir) + ctypes.sizeof(iconentry)
+
+    # Time to write everything out
+    out = open(outfile, "wb")
+    out.write(icondir)
+    out.write(iconentry)
+    out.write(outpngbuf)
+    out.close()
+
+if __name__ == "__main__":
+    # Convert left, top and size into integers
+    main(*([sys.argv[1]] + [int(val) for val in sys.argv[2:5]] + [sys.argv[5]]))
new file mode 100644
--- /dev/null
+++ b/build/pypng/exnumpy.py
@@ -0,0 +1,128 @@
+#!/usr/bin/env python
+# $URL: http://pypng.googlecode.com/svn/trunk/code/exnumpy.py $
+# $Rev: 126 $
+
+# Numpy example.
+# Original code created by Mel Raab, modified by David Jones.
+
+'''
+  Example code integrating RGB PNG files, PyPNG and NumPy
+  (abstracted from Mel Raab's functioning code)
+'''
+
+# http://www.python.org/doc/2.4.4/lib/module-itertools.html
+import itertools
+
+import numpy
+import png
+
+
+''' If you have a PNG file for an RGB image,
+    and want to create a numpy array of data from it.
+'''
+# Read the file "picture.png" from the current directory.  The `Reader`
+# class can take a filename, a file-like object, or the byte data
+# directly; this suggests alternatives such as using urllib to read
+# an image from the internet:
+# png.Reader(file=urllib.urlopen('http://www.libpng.org/pub/png/PngSuite/basn2c16.png'))
+pngReader=png.Reader(filename='picture.png')
+# Tuple unpacking, using multiple assignment, is very useful for the
+# result of asDirect (and other methods).
+# See
+# http://docs.python.org/tutorial/introduction.html#first-steps-towards-programming
+row_count, column_count, pngdata, meta = pngReader.asDirect()
+bitdepth=meta['bitdepth']
+plane_count=meta['planes']
+
+# Make sure we're dealing with RGB files
+assert plane_count == 3
+
+''' Boxed row flat pixel:
+      list([R,G,B, R,G,B, R,G,B],
+           [R,G,B, R,G,B, R,G,B])
+    Array dimensions for this example:  (2,9)
+
+    Create `image_2d` as a two-dimensional NumPy array by stacking a
+    sequence of 1-dimensional arrays (rows).
+    The NumPy array mimics PyPNG's (boxed row flat pixel) representation;
+    it will have dimensions ``(row_count,column_count*plane_count)``.
+'''
+# The use of ``numpy.uint16``, below, is to convert each row to a NumPy
+# array with data type ``numpy.uint16``.  This is a feature of NumPy,
+# discussed further in 
+# http://docs.scipy.org/doc/numpy/user/basics.types.html .
+# You can use avoid the explicit conversion with
+# ``numpy.vstack(pngdata)``, but then NumPy will pick the array's data
+# type; in practice it seems to pick ``numpy.int32``, which is large enough
+# to hold any pixel value for any PNG image but uses 4 bytes per value when
+# 1 or 2 would be enough.
+# --- extract 001 start
+image_2d = numpy.vstack(itertools.imap(numpy.uint16, pngdata))
+# --- extract 001 end
+# Do not be tempted to use ``numpy.asarray``; when passed an iterator
+# (`pngdata` is often an iterator) it will attempt to create a size 1
+# array with the iterator as its only element.
+# An alternative to the above is to create the target array of the right
+# shape, then populate it row by row:
+if 0:
+    image_2d = numpy.zeros((row_count,plane_count*column_count),
+                           dtype=numpy.uint16)
+    for row_index, one_boxed_row_flat_pixels in enumerate(pngdata):
+        image_2d[row_index,:]=one_boxed_row_flat_pixels
+
+del pngReader
+del pngdata
+
+
+''' Reconfigure for easier referencing, similar to
+        Boxed row boxed pixel:
+            list([ (R,G,B), (R,G,B), (R,G,B) ],
+                 [ (R,G,B), (R,G,B), (R,G,B) ])
+    Array dimensions for this example:  (2,3,3)
+
+    ``image_3d`` will contain the image as a three-dimensional numpy
+    array, having dimensions ``(row_count,column_count,plane_count)``.
+'''
+# --- extract 002 start
+image_3d = numpy.reshape(image_2d,
+                         (row_count,column_count,plane_count))
+# --- extract 002 end
+
+
+''' ============= '''
+
+''' Convert NumPy image_3d array to PNG image file.
+
+    If the data is three-dimensional, as it is above, the best thing
+    to do is reshape it into a two-dimensional array with a shape of
+    ``(row_count, column_count*plane_count)``.  Because a
+    two-dimensional numpy array is an iterator, it can be passed
+    directly to the ``png.Writer.write`` method.
+'''
+
+row_count, column_count, plane_count = image_3d.shape
+assert plane_count==3
+
+pngfile = open('picture_out.png', 'wb')
+try:
+    # This example assumes that you have 16-bit pixel values in the data
+    # array (that's what the ``bitdepth=16`` argument is for).
+    # If you don't, then the resulting PNG file will likely be
+    # very dark.  Hey, it's only an example.
+    pngWriter = png.Writer(column_count, row_count,
+                           greyscale=False,
+                           alpha=False,
+                           bitdepth=16)
+    # As of 2009-04-13 passing a numpy array that has an element type
+    # that is a numpy integer type (for example, the `image_3d` array has an
+    # element type of ``numpy.uint16``) generates a deprecation warning.
+    # This is probably a bug in numpy; it may go away in the future.
+    # The code still works despite the warning.
+    # See http://code.google.com/p/pypng/issues/detail?id=44
+# --- extract 003 start
+    pngWriter.write(pngfile,
+                    numpy.reshape(image_3d, (-1, column_count*plane_count)))
+# --- extract 003 end
+finally:
+    pngfile.close()
+
new file mode 100644
--- /dev/null
+++ b/build/pypng/iccp.py
@@ -0,0 +1,537 @@
+#!/usr/bin/env python
+# $URL: http://pypng.googlecode.com/svn/trunk/code/iccp.py $
+# $Rev: 182 $
+
+# iccp
+#
+# International Color Consortium Profile
+#
+# Tools for manipulating ICC profiles.
+#
+# An ICC profile can be extracted from a PNG image (iCCP chunk).
+#
+#
+# Non-standard ICCP tags.
+#
+# Apple use some (widespread but) non-standard tags.  These can be
+# displayed in Apple's ColorSync Utility.
+# - 'vcgt' (Video Card Gamma Tag).  Table to load into video
+#    card LUT to apply gamma.
+# - 'ndin' Apple display native information.
+# - 'dscm' Apple multi-localized description strings.
+# - 'mmod' Apple display make and model information.
+# 
+
+# References
+#
+# [ICC 2001] ICC Specification ICC.1:2001-04 (Profile version 2.4.0)
+# [ICC 2004] ICC Specification ICC.1:2004-10 (Profile version 4.2.0.0)
+
+import struct
+
+import png
+
+class FormatError(Exception):
+    pass
+
+class Profile:
+    """An International Color Consortium Profile (ICC Profile)."""
+
+    def __init__(self):
+        self.rawtagtable = None
+        self.rawtagdict = {}
+        self.d = dict()
+
+    def fromFile(self, inp, name='<unknown>'):
+
+        # See [ICC 2004]
+        profile = inp.read(128)
+        if len(profile) < 128:
+            raise FormatError("ICC Profile is too short.")
+        size, = struct.unpack('>L', profile[:4])
+        profile += inp.read(d['size'] - len(profile))
+        return self.fromString(profile, name)
+
+    def fromString(self, profile, name='<unknown>'):
+        self.d = dict()
+        d = self.d
+        if len(profile) < 128:
+            raise FormatError("ICC Profile is too short.")
+        d.update(
+          zip(['size', 'preferredCMM', 'version',
+               'profileclass', 'colourspace', 'pcs'],
+              struct.unpack('>L4sL4s4s4s', profile[:24])))
+        if len(profile) < d['size']:
+            warnings.warn(
+              'Profile size declared to be %d, but only got %d bytes' %
+                (d['size'], len(profile)))
+        d['version'] = '%08x' % d['version']
+        d['created'] = readICCdatetime(profile[24:36])
+        d.update(
+          zip(['acsp', 'platform', 'flag', 'manufacturer', 'model'],
+              struct.unpack('>4s4s3L', profile[36:56])))
+        if d['acsp'] != 'acsp':
+            warnings.warn('acsp field not present (not an ICC Profile?).')
+        d['deviceattributes'] = profile[56:64]
+        d['intent'], = struct.unpack('>L', profile[64:68])
+        d['pcsilluminant'] = readICCXYZNumber(profile[68:80])
+        d['creator'] = profile[80:84]
+        d['id'] = profile[84:100]
+        ntags, = struct.unpack('>L', profile[128:132])
+        d['ntags'] = ntags
+        fmt = '4s2L' * ntags
+        # tag table
+        tt = struct.unpack('>' + fmt, profile[132:132+12*ntags])
+        tt = group(tt, 3)
+
+        # Could (should) detect 2 or more tags having the same sig.  But
+        # we don't.  Two or more tags with the same sig is illegal per
+        # the ICC spec.
+        
+        # Convert (sig,offset,size) triples into (sig,value) pairs.
+        rawtag = map(lambda x: (x[0], profile[x[1]:x[1]+x[2]]), tt)
+        self.rawtagtable = rawtag
+        self.rawtagdict = dict(rawtag)
+        tag = dict()
+        # Interpret the tags whose types we know about
+        for sig, v in rawtag:
+            if sig in tag:
+                warnings.warn("Duplicate tag %r found.  Ignoring." % sig)
+                continue
+            v = ICCdecode(v)
+            if v is not None:
+                tag[sig] = v
+        self.tag = tag
+        return self
+
+    def greyInput(self):
+        """Adjust ``self.d`` dictionary for greyscale input device.
+        ``profileclass`` is 'scnr', ``colourspace`` is 'GRAY', ``pcs``
+        is 'XYZ '.
+        """
+
+        self.d.update(dict(profileclass='scnr',
+          colourspace='GRAY', pcs='XYZ '))
+        return self
+
+    def maybeAddDefaults(self):
+        if self.rawtagdict:
+            return
+        self._addTags(
+          cprt='Copyright unknown.',
+          desc='created by $URL: http://pypng.googlecode.com/svn/trunk/code/iccp.py $ $Rev: 182 $',
+          wtpt=D50(),
+          )
+
+    def addTags(self, **k):
+        self.maybeAddDefaults()
+        self._addTags(**k)
+
+    def _addTags(self, **k):
+        """Helper for :meth:`addTags`."""
+
+        for tag, thing in k.items():
+            if not isinstance(thing, (tuple, list)):
+                thing = (thing,)
+            typetag = defaulttagtype[tag]
+            self.rawtagdict[tag] = encode(typetag, *thing)
+        return self
+
+    def write(self, out):
+        """Write ICC Profile to the file."""
+
+        if not self.rawtagtable:
+            self.rawtagtable = self.rawtagdict.items()
+        tags = tagblock(self.rawtagtable)
+        self.writeHeader(out, 128 + len(tags))
+        out.write(tags)
+        out.flush()
+
+        return self
+
+    def writeHeader(self, out, size=999):
+        """Add default values to the instance's `d` dictionary, then
+        write a header out onto the file stream.  The size of the
+        profile must be specified using the `size` argument.
+        """
+
+        def defaultkey(d, key, value):
+            """Add ``[key]==value`` to the dictionary `d`, but only if
+            it does not have that key already.
+            """
+
+            if key in d:
+                return
+            d[key] = value
+
+        z = '\x00' * 4
+        defaults = dict(preferredCMM=z,
+                        version='02000000',
+                        profileclass=z,
+                        colourspace=z,
+                        pcs='XYZ ',
+                        created=writeICCdatetime(),
+                        acsp='acsp',
+                        platform=z,
+                        flag=0,
+                        manufacturer=z,
+                        model=0,
+                        deviceattributes=0,
+                        intent=0,
+                        pcsilluminant=encodefuns()['XYZ'](*D50()),
+                        creator=z,
+                        )
+        for k,v in defaults.items():
+            defaultkey(self.d, k, v)
+
+        hl = map(self.d.__getitem__,
+                 ['preferredCMM', 'version', 'profileclass', 'colourspace',
+                  'pcs', 'created', 'acsp', 'platform', 'flag',
+                  'manufacturer', 'model', 'deviceattributes', 'intent',
+                  'pcsilluminant', 'creator'])
+        # Convert to struct.pack input
+        hl[1] = int(hl[1], 16)
+
+        out.write(struct.pack('>L4sL4s4s4s12s4s4sL4sLQL12s4s', size, *hl))
+        out.write('\x00' * 44)
+        return self
+
+def encodefuns():
+    """Returns a dictionary mapping ICC type signature sig to encoding
+    function.  Each function returns a string comprising the content of
+    the encoded value.  To form the full value, the type sig and the 4
+    zero bytes should be prefixed (8 bytes).
+    """
+
+    def desc(ascii):
+        """Return textDescription type [ICC 2001] 6.5.17.  The ASCII part is
+        filled in with the string `ascii`, the Unicode and ScriptCode parts
+        are empty."""
+
+        ascii += '\x00'
+        l = len(ascii)
+
+        return struct.pack('>L%ds2LHB67s' % l,
+                           l, ascii, 0, 0, 0, 0, '')
+
+    def text(ascii):
+        """Return textType [ICC 2001] 6.5.18."""
+
+        return ascii + '\x00'
+
+    def curv(f=None, n=256):
+        """Return a curveType, [ICC 2001] 6.5.3.  If no arguments are
+        supplied then a TRC for a linear response is generated (no entries).
+        If an argument is supplied and it is a number (for *f* to be a
+        number it  means that ``float(f)==f``) then a TRC for that
+        gamma value is generated.
+        Otherwise `f` is assumed to be a function that maps [0.0, 1.0] to
+        [0.0, 1.0]; an `n` element table is generated for it.
+        """
+
+        if f is None:
+            return struct.pack('>L',  0)
+        try:
+            if float(f) == f:
+                return struct.pack('>LH', 1, int(round(f*2**8)))
+        except (TypeError, ValueError):
+            pass
+        assert n >= 2
+        table = []
+        M = float(n-1)
+        for i in range(n):
+            x = i/M
+            table.append(int(round(f(x) * 65535)))
+        return struct.pack('>L%dH' % n, n, *table)
+
+    def XYZ(*l):
+        return struct.pack('>3l', *map(fs15f16, l))
+
+    return locals()
+
+# Tag type defaults.
+# Most tags can only have one or a few tag types.
+# When encoding, we associate a default tag type with each tag so that
+# the encoding is implicit.
+defaulttagtype=dict(
+  A2B0='mft1',
+  A2B1='mft1',
+  A2B2='mft1',
+  bXYZ='XYZ',
+  bTRC='curv',
+  B2A0='mft1',
+  B2A1='mft1',
+  B2A2='mft1',
+  calt='dtim',
+  targ='text',
+  chad='sf32',
+  chrm='chrm',
+  cprt='desc',
+  crdi='crdi',
+  dmnd='desc',
+  dmdd='desc',
+  devs='',
+  gamt='mft1',
+  kTRC='curv',
+  gXYZ='XYZ',
+  gTRC='curv',
+  lumi='XYZ',
+  meas='',
+  bkpt='XYZ',
+  wtpt='XYZ',
+  ncol='',
+  ncl2='',
+  resp='',
+  pre0='mft1',
+  pre1='mft1',
+  pre2='mft1',
+  desc='desc',
+  pseq='',
+  psd0='data',
+  psd1='data',
+  psd2='data',
+  psd3='data',
+  ps2s='data',
+  ps2i='data',
+  rXYZ='XYZ',
+  rTRC='curv',
+  scrd='desc',
+  scrn='',
+  tech='sig',
+  bfd='',
+  vued='desc',
+  view='view',
+)
+
+def encode(tsig, *l):
+    """Encode a Python value as an ICC type.  `tsig` is the type
+    signature to (the first 4 bytes of the encoded value, see [ICC 2004]
+    section 10.
+    """
+
+    fun = encodefuns()
+    if tsig not in fun:
+        raise "No encoder for type %r." % tsig
+    v = fun[tsig](*l)
+    # Padd tsig out with spaces.
+    tsig = (tsig + '   ')[:4]
+    return tsig + '\x00'*4 + v
+
+def tagblock(tag):
+    """`tag` should be a list of (*signature*, *element*) pairs, where
+    *signature* (the key) is a length 4 string, and *element* is the
+    content of the tag element (another string).
+    
+    The entire tag block (consisting of first a table and then the
+    element data) is constructed and returned as a string.
+    """
+
+    n = len(tag)
+    tablelen = 12*n
+
+    # Build the tag table in two parts.  A list of 12-byte tags, and a
+    # string of element data.  Offset is the offset from the start of
+    # the profile to the start of the element data (so the offset for
+    # the next element is this offset plus the length of the element
+    # string so far).
+    offset = 128 + tablelen + 4
+    # The table.  As a string.
+    table = ''
+    # The element data
+    element = ''
+    for k,v in tag:
+        table += struct.pack('>4s2L', k, offset + len(element), len(v))
+        element += v
+    return struct.pack('>L', n) + table + element
+
+def iccp(out, inp):
+    profile = Profile().fromString(*profileFromPNG(inp))
+    print >>out, profile.d
+    print >>out, map(lambda x: x[0], profile.rawtagtable)
+    print >>out, profile.tag
+
+def profileFromPNG(inp):
+    """Extract profile from PNG file.  Return (*profile*, *name*)
+    pair."""
+    r = png.Reader(file=inp)
+    _,chunk = r.chunk('iCCP')
+    i = chunk.index('\x00')
+    name = chunk[:i]
+    compression = chunk[i+1]
+    assert compression == chr(0)
+    profile = chunk[i+2:].decode('zlib')
+    return profile, name
+
+def iccpout(out, inp):
+    """Extract ICC Profile from PNG file `inp` and write it to
+    the file `out`."""
+
+    out.write(profileFromPNG(inp)[0])
+
+def fs15f16(x):
+    """Convert float to ICC s15Fixed16Number (as a Python ``int``)."""
+
+    return int(round(x * 2**16))
+
+def D50():
+    """Return D50 illuminant as an (X,Y,Z) triple."""
+
+    # See [ICC 2001] A.1
+    return (0.9642, 1.0000, 0.8249)
+
+
+def writeICCdatetime(t=None):
+    """`t` should be a gmtime tuple (as returned from
+    ``time.gmtime()``).  If not supplied, the current time will be used.
+    Return an ICC dateTimeNumber in a 12 byte string.
+    """
+
+    import time
+    if t is None:
+        t = time.gmtime()
+    return struct.pack('>6H', *t[:6])
+
+def readICCdatetime(s):
+    """Convert from 12 byte ICC representation of dateTimeNumber to
+    ISO8601 string. See [ICC 2004] 5.1.1"""
+
+    return '%04d-%02d-%02dT%02d:%02d:%02dZ' % struct.unpack('>6H', s)
+
+def readICCXYZNumber(s):
+    """Convert from 12 byte ICC representation of XYZNumber to (x,y,z)
+    triple of floats.  See [ICC 2004] 5.1.11"""
+
+    return s15f16l(s)
+
+def s15f16l(s):
+    """Convert sequence of ICC s15Fixed16 to list of float."""
+    # Note: As long as float has at least 32 bits of mantissa, all
+    # values are preserved.
+    n = len(s)//4
+    t = struct.unpack('>%dl' % n, s)
+    return map((2**-16).__mul__, t)
+
+# Several types and their byte encodings are defined by [ICC 2004]
+# section 10.  When encoded, a value begins with a 4 byte type
+# signature.  We use the same 4 byte type signature in the names of the
+# Python functions that decode the type into a Pythonic representation.
+
+def ICCdecode(s):
+    """Take an ICC encoded tag, and dispatch on its type signature
+    (first 4 bytes) to decode it into a Python value.  Pair (*sig*,
+    *value*) is returned, where *sig* is a 4 byte string, and *value* is
+    some Python value determined by the content and type.
+    """
+
+    sig = s[0:4].strip()
+    f=dict(text=RDtext,
+           XYZ=RDXYZ,
+           curv=RDcurv,
+           vcgt=RDvcgt,
+           sf32=RDsf32,
+           )
+    if sig not in f:
+        return None
+    return (sig, f[sig](s))
+
+def RDXYZ(s):
+    """Convert ICC XYZType to rank 1 array of trimulus values."""
+
+    # See [ICC 2001] 6.5.26
+    assert s[0:4] == 'XYZ '
+    return readICCXYZNumber(s[8:])
+
+def RDsf32(s):
+    """Convert ICC s15Fixed16ArrayType to list of float."""
+    # See [ICC 2004] 10.18
+    assert s[0:4] == 'sf32'
+    return s15f16l(s[8:])
+
+def RDmluc(s):
+    """Convert ICC multiLocalizedUnicodeType.  This types encodes
+    several strings together with a language/country code for each
+    string.  A list of (*lc*, *string*) pairs is returned where *lc* is
+    the 4 byte language/country code, and *string* is the string
+    corresponding to that code.  It seems unlikely that the same
+    language/country code will appear more than once with different
+    strings, but the ICC standard does not prohibit it."""
+    # See [ICC 2004] 10.13
+    assert s[0:4] == 'mluc'
+    n,sz = struct.unpack('>2L', s[8:16])
+    assert sz == 12
+    record = []
+    for i in range(n):
+        lc,l,o = struct.unpack('4s2L', s[16+12*n:28+12*n])
+        record.append(lc, s[o:o+l])
+    # How are strings encoded?
+    return record
+
+def RDtext(s):
+    """Convert ICC textType to Python string."""
+    # Note: type not specified or used in [ICC 2004], only in older
+    # [ICC 2001].
+    # See [ICC 2001] 6.5.18
+    assert s[0:4] == 'text'
+    return s[8:-1]
+
+def RDcurv(s):
+    """Convert ICC curveType."""
+    # See [ICC 2001] 6.5.3
+    assert s[0:4] == 'curv'
+    count, = struct.unpack('>L', s[8:12])
+    if count == 0:
+        return dict(gamma=1)
+    table = struct.unpack('>%dH' % count, s[12:])
+    if count == 1:
+        return dict(gamma=table[0]*2**-8)
+    return table
+
+def RDvcgt(s):
+    """Convert Apple CMVideoCardGammaType."""
+    # See
+    # http://developer.apple.com/documentation/GraphicsImaging/Reference/ColorSync_Manager/Reference/reference.html#//apple_ref/c/tdef/CMVideoCardGammaType
+    assert s[0:4] == 'vcgt'
+    tagtype, = struct.unpack('>L', s[8:12])
+    if tagtype != 0:
+        return s[8:]
+    if tagtype == 0:
+        # Table.
+        channels,count,size = struct.unpack('>3H', s[12:18])
+        if size == 1:
+            fmt = 'B'
+        elif size == 2:
+            fmt = 'H'
+        else:
+            return s[8:]
+        l = len(s[18:])//size
+        t = struct.unpack('>%d%s' % (l, fmt), s[18:])
+        t = group(t, count)
+        return size, t
+    return s[8:]
+
+
+def group(s, n):
+    # See
+    # http://www.python.org/doc/2.6/library/functions.html#zip
+    return zip(*[iter(s)]*n)
+
+
+def main(argv=None):
+    import sys
+    from getopt import getopt
+    if argv is None:
+        argv = sys.argv
+    argv = argv[1:]
+    opt,arg = getopt(argv, 'o:')
+    if len(arg) > 0:
+        inp = open(arg[0], 'rb')
+    else:
+        inp = sys.stdin
+    for o,v in opt:
+        if o == '-o':
+            f = open(v, 'wb')
+            return iccpout(f, inp)
+    return iccp(sys.stdout, inp)
+
+if __name__ == '__main__':
+    main()
new file mode 100644
--- /dev/null
+++ b/build/pypng/mkiccp.py
@@ -0,0 +1,45 @@
+#!/usr/bin/env python
+# $URL: http://pypng.googlecode.com/svn/trunk/code/mkiccp.py $
+# $Rev: 182 $
+# Make ICC Profile
+
+# References
+#
+# [ICC 2001] ICC Specification ICC.1:2001-04 (Profile version 2.4.0)
+# [ICC 2004] ICC Specification ICC.1:2004-10 (Profile version 4.2.0.0)
+
+import struct
+
+# Local module.
+import iccp
+
+def black(m):
+    """Return a function that maps all values from [0.0,m] to 0, and maps
+    the range [m,1.0] into [0.0, 1.0] linearly.
+    """
+
+    m = float(m)
+
+    def f(x):
+        if x <= m:
+            return 0.0
+        return (x-m)/(1.0-m)
+    return f
+
+# For monochrome input the required tags are (See [ICC 2001] 6.3.1.1):
+# profileDescription [ICC 2001] 6.4.32
+# grayTRC [ICC 2001] 6.4.19
+# mediaWhitePoint [ICC 2001] 6.4.25
+# copyright [ICC 2001] 6.4.13
+
+def agreyprofile(out):
+    it = iccp.Profile().greyInput()
+    it.addTags(kTRC=black(0.07))
+    it.write(out)
+
+def main():
+    import sys
+    agreyprofile(sys.stdout)
+
+if __name__ == '__main__':
+    main()
new file mode 100644
--- /dev/null
+++ b/build/pypng/pdsimgtopng
@@ -0,0 +1,99 @@
+#!/usr/bin/env python
+# $URL: http://pypng.googlecode.com/svn/trunk/code/pdsimgtopng $
+# $Rev: 154 $
+# PDS Image to PNG
+
+import re
+import struct
+
+import png
+
+class FormatError(Exception):
+    pass
+
+def pdskey(s, k):
+    """Lookup key `k` in string `s`.  Returns value (as a string), or
+    raises exception if not found.
+    """
+
+    assert re.match(r' *\^?[:\w]+$', k)
+    safere = '^' + re.escape(k) +r' *= *(\w+)'
+    m = re.search(safere, s, re.MULTILINE)
+    if not m:
+        raise FormatError("Can't find %s." % k)
+    return m.group(1)
+
+def img(inp):
+    """Open the PDS IMG file `inp` and return (*pixels*, *info*).
+    *pixels* is an iterator over the rows, *info* is the information
+    dictionary.
+    """
+
+    err = __import__('sys').stderr
+
+    consumed = 1024
+
+    s = inp.read(consumed)
+    record_type = pdskey(s, 'RECORD_TYPE')
+    if record_type != 'FIXED_LENGTH':
+        raise FormatError(
+          "Can only deal with FIXED_LENGTH record type (found %s)" %
+            record_type)
+    record_bytes = int(pdskey(s,'RECORD_BYTES'))
+    file_records = int(pdskey(s, 'FILE_RECORDS'))
+    label_records = int(pdskey(s, 'LABEL_RECORDS'))
+    remaining = label_records * record_bytes - consumed
+    s += inp.read(remaining)
+    consumed += remaining
+
+    image_pointer = int(pdskey(s, '^IMAGE'))
+    # "^IMAGE" locates a record.  Records are numbered starting from 1.
+    image_index = image_pointer - 1
+    image_offset = image_index * record_bytes
+    gap = image_offset - consumed
+    assert gap >= 0
+    if gap:
+        inp.read(gap)
+    # This assumes there is only one OBJECT in the file, and it is the
+    # IMAGE.
+    height = int(pdskey(s, '  LINES'))
+    width = int(pdskey(s, '  LINE_SAMPLES'))
+    sample_type = pdskey(s, '  SAMPLE_TYPE')
+    sample_bits = int(pdskey(s, '  SAMPLE_BITS'))
+    # For Messenger MDIS, SAMPLE_BITS is reported as 16, but only values
+    # from 0 ot 4095 are used.
+    bitdepth = 12
+    if sample_type == 'MSB_UNSIGNED_INTEGER':
+        fmt = '>H'
+    else:
+        raise 'Unknown sample type: %s.' % sample_type
+    sample_bytes = (1,2)[bitdepth > 8]
+    row_bytes = sample_bytes * width
+    fmt = fmt[:1] + str(width) + fmt[1:]
+    def rowiter():
+        for y in range(height):
+            yield struct.unpack(fmt, inp.read(row_bytes))
+    info = dict(greyscale=True, alpha=False, bitdepth=bitdepth,
+      size=(width,height), gamma=1.0)
+    return rowiter(), info
+
+
+def main(argv=None):
+    import sys
+
+    if argv is None:
+        argv = sys.argv
+    argv = argv[1:]
+    arg = argv
+    if len(arg) >= 1:
+        f = open(arg[0], 'rb')
+    else:
+        f = sys.stdin
+    pixels,info = img(f)
+    w = png.Writer(**info)
+    w.write(sys.stdout, pixels)
+
+if __name__ == '__main__':
+    main()
+
+
new file mode 100644
--- /dev/null
+++ b/build/pypng/pipasgrey
@@ -0,0 +1,73 @@
+#!/usr/bin/env python
+# $URL: http://pypng.googlecode.com/svn/trunk/code/pipasgrey $
+# $Rev: 187 $
+
+# pipasgrey
+
+# Convert image to grey (L, or LA), but only if that involves no colour
+# change.
+
+def asgrey(out, inp, quiet=False):
+    """Convert image to greyscale, but only when no colour change.  This
+    works by using the input G channel (green) as the output L channel
+    (luminance) and checking that every pixel is grey as we go.  A non-grey
+    pixel will raise an error, but if `quiet` is true then the grey pixel
+    check is suppressed.
+    """
+
+    from array import array
+
+    import png
+
+    r = png.Reader(file=inp)
+    _,_,pixels,info = r.asDirect()
+    if info['greyscale']:
+        w = png.Writer(**info)
+        return w.write(out, pixels)
+    planes = info['planes']
+    targetplanes = planes - 2
+    alpha = info['alpha']
+    width = info['size'][0]
+    typecode = 'BH'[info['bitdepth'] > 8]
+    # Values per target row
+    vpr = width * (targetplanes)
+    def iterasgrey():
+        for i,row in enumerate(pixels):
+            row = array(typecode, row)
+            targetrow = array(typecode, [0]*vpr)
+            # Copy G (and possibly A) channel.
+            green = row[0::planes]
+            if alpha:
+                targetrow[0::2] = green
+                targetrow[1::2] = row[3::4]
+            else:
+                targetrow = green
+            # Check R and B channel match.
+            if not quiet and (
+              green != row[0::planes] or green != row[2::planes]):
+                raise ValueError('Row %i contains non-grey pixel.' % i)
+            yield targetrow
+    info['greyscale'] = True
+    del info['planes']
+    w = png.Writer(**info)
+    w.write(out, iterasgrey())
+
+def main(argv=None):
+    from getopt import getopt
+    import sys
+    if argv is None:
+        argv = sys.argv
+    argv = argv[1:]
+    opt,argv = getopt(argv, 'q')
+    quiet = False
+    for o,v in opt:
+        if o == '-q':
+            quiet = True
+    if len(argv) > 0:
+        f = open(argv[0], 'rb')
+    else:
+        f = sys.stdin
+    return asgrey(sys.stdout, f, quiet)
+
+if __name__ == '__main__':
+    main()
new file mode 100644
--- /dev/null
+++ b/build/pypng/pipcat
@@ -0,0 +1,44 @@
+#!/usr/bin/env python
+# $URL: http://pypng.googlecode.com/svn/trunk/code/pipcat $
+# $Rev: 77 $
+
+# http://www.python.org/doc/2.4.4/lib/module-itertools.html
+import itertools
+import sys
+
+import png
+
+def cat(out, l):
+    """Concatenate the list of images.  All input images must be same
+    height and have the same number of channels.  They are concatenated
+    left-to-right.  `out` is the (open file) destination for the
+    output image.  `l` should be a list of open files (the input
+    image files).
+    """
+
+    l = map(lambda f: png.Reader(file=f), l)
+    # Ewgh, side effects.
+    map(lambda r: r.preamble(), l)
+    # The reference height; from the first image.
+    height = l[0].height
+    # The total target width
+    width = 0
+    for i,r in enumerate(l):
+        if r.height != height:
+            raise Error('Image %d, height %d, does not match %d.' %
+              (i, r.height, height))
+        width += r.width
+    pixel,info = zip(*map(lambda r: r.asDirect()[2:4], l))
+    tinfo = dict(info[0])
+    del tinfo['size']
+    w = png.Writer(width, height, **tinfo)
+    def itercat():
+        for row in itertools.izip(*pixel):
+            yield itertools.chain(*row)
+    w.write(out, itercat())
+
+def main(argv):
+    return cat(sys.stdout, map(lambda n: open(n, 'rb'), argv[1:]))
+
+if __name__ == '__main__':
+    main(sys.argv)
new file mode 100644
--- /dev/null
+++ b/build/pypng/pipcolours
@@ -0,0 +1,56 @@
+#!/usr/bin/env python
+# $URL: http://pypng.googlecode.com/svn/trunk/code/pipcolours $
+# $Rev: 96 $
+
+# pipcolours - extract all colours present in source image.
+
+def colours(out, inp):
+    import itertools
+    import png
+
+    r = png.Reader(file=inp)
+    _,_,pixels,info = r.asDirect()
+    planes = info['planes']
+    col = set()
+    for row in pixels:
+        # Ewgh, side effects on col
+        map(col.add, png.group(row, planes))
+    col,planes = channel_reduce(col, planes)
+    col = list(col)
+    col.sort()
+    col = list(itertools.chain(*col))
+    width = len(col)//planes
+    greyscale = planes in (1,2)
+    alpha = planes in (2,4)
+    bitdepth = info['bitdepth']
+    w = png.Writer(width, 1,
+        bitdepth=bitdepth, greyscale=greyscale, alpha=alpha)
+    w.write(out, [col])
+
+def channel_reduce(col, planes):
+    """Attempt to reduce the number of channels in the set of
+    colours."""
+    if planes >= 3:
+        def isgrey(c):
+            return c[0] == c[1] == c[2]
+        if min(map(isgrey, col)) == True:
+            # Every colour is grey.
+            col = set(map(lambda x: x[0::3], col))
+            planes -= 2
+    return col,planes
+
+def main(argv=None):
+    import sys
+
+    if argv is None:
+        argv = sys.argv
+
+    argv = argv[1:]
+    if len(argv) > 0:
+        f = open(argv[0], 'rb')
+    else:
+        f = sys.stdin
+    return colours(sys.stdout, f)
+
+if __name__ == '__main__':
+    main()
new file mode 100644
--- /dev/null
+++ b/build/pypng/pipcomposite
@@ -0,0 +1,121 @@
+#!/usr/bin/env python
+# $URL: http://pypng.googlecode.com/svn/trunk/code/pipcomposite $
+# $Rev: 208 $
+# pipcomposite
+# Image alpha compositing.
+
+"""
+pipcomposite [--background #rrggbb] file.png
+
+Composite an image onto a background and output the result.  The
+background colour is specified with an HTML-style triple (3, 6, or 12
+hex digits), and defaults to black (#000).
+
+The output PNG has no alpha channel.
+
+It is valid for the input to have no alpha channel, but it doesn't
+make much sense: the output will equal the input.
+"""
+
+import sys
+
+def composite(out, inp, background):
+    import png
+
+    p = png.Reader(file=inp)
+    w,h,pixel,info = p.asRGBA()
+
+    outinfo = dict(info)
+    outinfo['alpha'] = False
+    outinfo['planes'] -= 1
+    outinfo['interlace'] = 0
+
+    # Convert to tuple and normalise to same range as source.
+    background = rgbhex(background)
+    maxval = float(2**info['bitdepth'] - 1)
+    background = map(lambda x: int(0.5 + x*maxval/65535.0),
+                     background)
+    # Repeat background so that it's a whole row of sample values.
+    background *= w
+
+    def iterrow():
+        for row in pixel:
+            # Remove alpha from row, then create a list with one alpha
+            # entry _per channel value_.
+            # Squirrel the alpha channel away (and normalise it).
+            t = map(lambda x: x/maxval, row[3::4])
+            row = list(row)
+            del row[3::4]
+            alpha = row[:]
+            for i in range(3):
+                alpha[i::3] = t
+            assert len(alpha) == len(row) == len(background)
+            yield map(lambda a,v,b: int(0.5 + a*v + (1.0-a)*b),
+                      alpha, row, background)
+
+    w = png.Writer(**outinfo)
+    w.write(out, iterrow())
+
+def rgbhex(s):
+    """Take an HTML style string of the form "#rrggbb" and return a
+    colour (R,G,B) triple.  Following the initial '#' there can be 3, 6,
+    or 12 digits (for 4-, 8- or 16- bits per channel).  In all cases the
+    values are expanded to a full 16-bit range, so the returned values
+    are all in range(65536).
+    """
+
+    assert s[0] == '#'
+    s = s[1:]
+    assert len(s) in (3,6,12)
+
+    # Create a target list of length 12, and expand the string s to make
+    # it length 12.
+    l = ['z']*12
+    if len(s) == 3:
+        for i in range(4):
+            l[i::4] = s
+    if len(s) == 6:
+        for i in range(2):
+            l[i::4] = s[i::2]
+            l[i+2::4] = s[i::2]
+    if len(s) == 12:
+        l[:] = s
+    s = ''.join(l)
+    return map(lambda x: int(x, 16), (s[:4], s[4:8], s[8:]))
+
+class Usage(Exception):
+    pass
+
+def main(argv=None):
+    import getopt
+    import sys
+
+    if argv is None:
+        argv = sys.argv
+
+    argv = argv[1:]
+
+    try:
+        try:
+            opt,arg = getopt.getopt(argv, '',
+                                    ['background='])
+        except getopt.error, msg:
+            raise Usage(msg)
+        background = '#000'
+        for o,v in opt:
+            if o in ['--background']:
+                background = v
+    except Usage, err:
+        print >>sys.stderr, __doc__
+        print >>sys.stderr, str(err)
+        return 2
+
+    if len(arg) > 0:
+        f = open(arg[0], 'rb')
+    else:
+        f = sys.stdin
+    return composite(sys.stdout, f, background)
+
+
+if __name__ == '__main__':
+    main()
new file mode 100644
--- /dev/null
+++ b/build/pypng/pipdither
@@ -0,0 +1,181 @@
+#!/usr/bin/env python
+# $URL: http://pypng.googlecode.com/svn/trunk/code/pipdither $
+# $Rev: 150 $
+
+# pipdither
+# Error Diffusing image dithering.
+# Now with serpentine scanning.
+
+# See http://www.efg2.com/Lab/Library/ImageProcessing/DHALF.TXT
+
+# http://www.python.org/doc/2.4.4/lib/module-bisect.html
+from bisect import bisect_left
+
+import png
+
+def dither(out, inp,
+  bitdepth=1, linear=False, defaultgamma=1.0, targetgamma=None,
+  cutoff=0.75):
+    """Dither the input PNG `inp` into an image with a smaller bit depth
+    and write the result image onto `out`.  `bitdepth` specifies the bit
+    depth of the new image.
+    
+    Normally the source image gamma is honoured (the image is
+    converted into a linear light space before being dithered), but
+    if the `linear` argument is true then the image is treated as
+    being linear already: no gamma conversion is done (this is
+    quicker, and if you don't care much about accuracy, it won't
+    matter much).
+    
+    Images with no gamma indication (no ``gAMA`` chunk) are normally
+    treated as linear (gamma = 1.0), but often it can be better
+    to assume a different gamma value: For example continuous tone
+    photographs intended for presentation on the web often carry
+    an implicit assumption of being encoded with a gamma of about
+    0.45 (because that's what you get if you just "blat the pixels"
+    onto a PC framebuffer), so ``defaultgamma=0.45`` might be a
+    good idea.  `defaultgamma` does not override a gamma value
+    specified in the file itself: It is only used when the file
+    does not specify a gamma.
+
+    If you (pointlessly) specify both `linear` and `defaultgamma`,
+    `linear` wins.
+
+    The gamma of the output image is, by default, the same as the input
+    image.  The `targetgamma` argument can be used to specify a
+    different gamma for the output image.  This effectively recodes the
+    image to a different gamma, dithering as we go.  The gamma specified
+    is the exponent used to encode the output file (and appears in the
+    output PNG's ``gAMA`` chunk); it is usually less than 1.
+
+    """
+
+    # Encoding is what happened when the PNG was made (and also what
+    # happens when we output the PNG).  Decoding is what we do to the
+    # source PNG in order to process it.
+
+    # The dithering algorithm is not completely general; it
+    # can only do bit depth reduction, not arbitrary palette changes.
+    import operator
+    maxval = 2**bitdepth - 1
+    r = png.Reader(file=inp)
+    # If image gamma is 1 or gamma is not present and we are assuming a
+    # value of 1, then it is faster to pass a maxval parameter to
+    # asFloat (the multiplications get combined).  With gamma, we have
+    # to have the pixel values from 0.0 to 1.0 (as long as we are doing
+    # gamma correction here).
+    # Slightly annoyingly, we don't know the image gamma until we've
+    # called asFloat().
+    _,_,pixels,info = r.asDirect()
+    planes = info['planes']
+    assert planes == 1
+    width = info['size'][0]
+    sourcemaxval = 2**info['bitdepth'] - 1
+    if linear:
+        gamma = 1
+    else:
+        gamma = info.get('gamma') or defaultgamma
+    # Convert gamma from encoding gamma to the required power for
+    # decoding.
+    decode = 1.0/gamma
+    # Build a lookup table for decoding; convert from pixel values to linear
+    # space:
+    sourcef = 1.0/sourcemaxval
+    incode = map(sourcef.__mul__, range(sourcemaxval+1))
+    if decode != 1.0:
+        incode = map(decode.__rpow__, incode)
+    # Could be different, later on.  targetdecode is the assumed gamma
+    # that is going to be used to decoding the target PNG.  It is the
+    # reciprocal of the exponent that we use to encode the target PNG.
+    # This is the value that we need to build our table that we use for
+    # converting from linear to target colour space.
+    if targetgamma is None:
+        targetdecode = decode
+    else:
+        targetdecode = 1.0/targetgamma
+    # The table we use for encoding (creating the target PNG), still
+    # maps from pixel value to linear space, but we use it inverted, by
+    # searching through it with bisect.
+    targetf = 1.0/maxval
+    outcode = map(targetf.__mul__, range(maxval+1))
+    if targetdecode != 1.0:
+        outcode = map(targetdecode.__rpow__, outcode)
+    # The table used for choosing output codes.  These values represent
+    # the cutoff points between two adjacent output codes.
+    choosecode = zip(outcode[1:], outcode)
+    p = cutoff
+    choosecode = map(lambda x: x[0]*p+x[1]*(1.0-p), choosecode)
+    def iterdither():
+        # Errors diffused downwards (into next row)
+        ed = [0.0]*width
+        flipped = False
+        for row in pixels:
+            row = map(incode.__getitem__, row)
+            row = map(operator.add, ed, row)
+            if flipped:
+                row = row[::-1]
+            targetrow = [0] * width
+            for i,v in enumerate(row):
+                # Clamp.  Necessary because previously added errors may take
+                # v out of range.
+                v = max(0.0, min(v, 1.0))
+                # `it` will be the index of the chosen target colour;
+                it = bisect_left(choosecode, v)
+                t = outcode[it]
+                targetrow[i] = it
+                # err is the error that needs distributing.
+                err = v - t
+                # Sierra "Filter Lite" distributes          * 2
+                # as per this diagram.                    1 1
+                ef = err/2.0
+                # :todo: consider making rows one wider at each end and
+                # removing "if"s
+                if i+1 < width:
+                    row[i+1] += ef
+                ef /= 2.0
+                ed[i] = ef
+                if i:
+                    ed[i-1] += ef
+            if flipped:
+                ed = ed[::-1]
+                targetrow = targetrow[::-1]
+            yield targetrow
+            flipped = not flipped
+    info['bitdepth'] = bitdepth
+    info['gamma'] = 1.0/targetdecode
+    w = png.Writer(**info)
+    w.write(out, iterdither())
+
+
+def main(argv=None):
+    # http://www.python.org/doc/2.4.4/lib/module-getopt.html
+    from getopt import getopt
+    import sys
+    if argv is None:
+        argv = sys.argv
+    opt,argv = getopt(argv[1:], 'b:c:g:lo:')
+    k = {}
+    for o,v in opt:
+        if o == '-b':
+            k['bitdepth'] = int(v)
+        if o == '-c':
+            k['cutoff'] = float(v)
+        if o == '-g':
+            k['defaultgamma'] = float(v)
+        if o == '-l':
+            k['linear'] = True
+        if o == '-o':
+            k['targetgamma'] = float(v)
+        if o == '-?':
+            print >>sys.stderr, "pipdither [-b bits] [-c cutoff] [-g assumed-gamma] [-l] [in.png]"
+
+    if len(argv) > 0:
+        f = open(argv[0], 'rb')
+    else:
+        f = sys.stdin
+
+    return dither(sys.stdout, f, **k)
+
+
+if __name__ == '__main__':
+    main()
new file mode 100644
--- /dev/null
+++ b/build/pypng/piprgb
@@ -0,0 +1,36 @@
+#!/usr/bin/env python
+# $URL: http://pypng.googlecode.com/svn/trunk/code/piprgb $
+# $Rev: 131 $
+# piprgb
+#
+# Convert input image to RGB or RGBA format.  Output will be colour type
+# 2 or 6, and will not have a tRNS chunk.
+
+import png
+
+def rgb(out, inp):
+    """Convert to RGB/RGBA."""
+
+    r = png.Reader(file=inp)
+    r.preamble()
+    if r.alpha or r.trns:
+        get = r.asRGBA
+    else:
+        get = r.asRGB
+    pixels,info = get()[2:4]
+    w = png.Writer(**info)
+    w.write(out, pixels)
+
+def main(argv=None):
+    import sys
+
+    if argv is None:
+        argv = sys.argv
+    if len(argv) > 1:
+        f = open(argv[1], 'rb')
+    else:
+        f = sys.stdin
+    return rgb(sys.stdout, f)
+
+if __name__ == '__main__':
+    main()
new file mode 100644
--- /dev/null
+++ b/build/pypng/pipscalez
@@ -0,0 +1,53 @@
+#!/usr/bin/env python
+# $URL: http://pypng.googlecode.com/svn/trunk/code/pipscalez $
+# $Rev: 131 $
+
+# pipscalez
+# Enlarge an image by an integer factor horizontally and vertically.
+
+def rescale(inp, out, xf, yf):
+    from array import array
+    import png
+
+    r = png.Reader(file=inp)
+    _,_,pixels,meta = r.asDirect()
+    typecode = 'BH'[meta['bitdepth'] > 8]
+    planes = meta['planes']
+    # We are going to use meta in the call to Writer, so expand the
+    # size.
+    x,y = meta['size']
+    x *= xf
+    y *= yf
+    meta['size'] = (x,y)
+    del x
+    del y
+    # Values per row, target row.
+    vpr = meta['size'][0] * planes
+    def iterscale():
+        for row in pixels:
+            bigrow = array(typecode, [0]*vpr)
+            row = array(typecode, row)
+            for c in range(planes):
+                channel = row[c::planes]
+                for i in range(xf):
+                    bigrow[i*planes+c::xf*planes] = channel
+            for _ in range(yf):
+                yield bigrow
+    w = png.Writer(**meta)
+    w.write(out, iterscale())
+
+
+def main(argv=None):
+    import sys
+
+    if argv is None:
+        argv = sys.argv
+    xf = int(argv[1])
+    if len(argv) > 2:
+        yf = int(argv[2])
+    else:
+        yf = xf
+    return rescale(sys.stdin, sys.stdout, xf, yf)
+
+if __name__ == '__main__':
+    main()
new file mode 100644
--- /dev/null
+++ b/build/pypng/pipstack
@@ -0,0 +1,127 @@
+#!/usr/bin/env python
+# $URL: http://pypng.googlecode.com/svn/trunk/code/pipstack $
+# $Rev: 190 $
+
+# pipstack
+# Combine input PNG files into a multi-channel output PNG.
+
+"""
+pipstack file1.png [file2.png ...]
+
+pipstack can be used to combine 3 greyscale PNG files into a colour, RGB,
+PNG file.  In fact it is slightly more general than that.  The number of
+channels in the output PNG is equal to the sum of the numbers of
+channels in the input images.  It is an error if this sum exceeds 4 (the
+maximum number of channels in a PNG image is 4, for an RGBA image).  The
+output colour model corresponds to the number of channels: 1 -
+greyscale; 2 - greyscale+alpha; 3 - RGB; 4 - RGB+alpha.
+
+In this way it is possible to combine 3 greyscale PNG files into an RGB
+PNG (a common expected use) as well as more esoteric options: rgb.png +
+grey.png = rgba.png; grey.png + grey.png = greyalpha.png.
+
+Color Profile, Gamma, and so on.
+
+[This is not implemented yet]
+
+If an input has an ICC Profile (``iCCP`` chunk) then the output will
+have an ICC Profile, but only if it is possible to combine all the input
+ICC Profiles.  It is possible to combine all the input ICC Profiles
+only when: they all use the same Profile Connection Space; the PCS white
+point is the same (specified in the header; should always be D50);
+possibly some other things I haven't thought of yet.
+
+If some of the inputs have a ``gAMA`` chunk (specifying gamma) and
+an output ICC Profile is being generated, then the gamma information
+will be incorporated into the ICC Profile.
+
+When the output is an RGB colour type and the output ICC Profile is
+synthesized, it is necessary to supply colorant tags (``rXYZ`` and so
+on).  These are taken from ``sRGB``.
+
+If the input images have ``gAMA`` chunks and no input image has an ICC
+Profile then the output image will have a ``gAMA`` chunk, but only if
+all the ``gAMA`` chunks specify the same value.  Otherwise a warning
+will be emitted and no ``gAMA`` chunk.  It is possible to add or replace
+a ``gAMA`` chunk using the ``pipchunk`` tool.
+
+gAMA, pHYs, iCCP, sRGB, tIME, any other chunks.
+"""
+
+class Error(Exception):
+    pass
+
+def stack(out, inp):
+    """Stack the input PNG files into a single output PNG."""
+
+    from array import array
+    import itertools
+    # Local module
+    import png
+
+    if len(inp) < 1:
+        raise Error("Required input is missing.")
+
+    l = map(png.Reader, inp)
+    # Let data be a list of (pixel,info) pairs.
+    data = map(lambda p: p.asDirect()[2:], l)
+    totalchannels = sum(map(lambda x: x[1]['planes'], data))
+
+    if not (0 < totalchannels <= 4):
+        raise Error("Too many channels in input.")
+    alpha = totalchannels in (2,4)
+    greyscale = totalchannels in (1,2)
+    bitdepth = []
+    for b in map(lambda x: x[1]['bitdepth'], data):
+        try:
+            if b == int(b):
+                bitdepth.append(b)
+                continue
+        except (TypeError, ValueError):
+            pass
+        # Assume a tuple.
+        bitdepth += b
+    # Currently, fail unless all bitdepths equal.
+    if len(set(bitdepth)) > 1:
+        raise NotImplemented("Cannot cope when bitdepths differ - sorry!")
+    bitdepth = bitdepth[0]
+    arraytype = 'BH'[bitdepth > 8]
+    size = map(lambda x: x[1]['size'], data)
+    # Currently, fail unless all images same size.
+    if len(set(size)) > 1:
+        raise NotImplemented("Cannot cope when sizes differ - sorry!")
+    size = size[0]
+    # Values per row
+    vpr = totalchannels * size[0]
+    def iterstack():
+        # the izip call creates an iterator that yields the next row
+        # from all the input images combined into a tuple.
+        for irow in itertools.izip(*map(lambda x: x[0], data)):
+            row = array(arraytype, [0]*vpr)
+            # output channel
+            och = 0
+            for i,arow in enumerate(irow):
+                # ensure incoming row is an array
+                arow = array(arraytype, arow)
+                n = data[i][1]['planes']
+                for j in range(n):
+                    row[och::totalchannels] = arow[j::n]
+                    och += 1
+            yield row
+    w = png.Writer(size[0], size[1],
+      greyscale=greyscale, alpha=alpha, bitdepth=bitdepth)
+    w.write(out, iterstack())
+
+
+def main(argv=None):
+    import sys
+
+    if argv is None:
+        argv = sys.argv
+    argv = argv[1:]
+    arg = argv[:]
+    return stack(sys.stdout, arg)
+
+
+if __name__ == '__main__':
+    main()
new file mode 100644
--- /dev/null
+++ b/build/pypng/pipwindow
@@ -0,0 +1,67 @@
+#!/usr/bin/env python
+# $URL: http://pypng.googlecode.com/svn/trunk/code/pipwindow $
+# $Rev: 173 $
+
+# pipwindow
+# Tool to crop/expand an image to a rectangular window.  Come the
+# revolution this tool will allow the image and the window to be placed
+# arbitrarily (in particular the window can be bigger than the picture
+# and/or overlap it only partially) and the image can be OpenGL style
+# border/repeat effects (repeat, mirrored repeat, clamp, fixed
+# background colour, background colour from source file).  For now it
+# only acts as crop.  The window must be no greater than the image in
+# both x and y.
+
+def window(tl, br, inp, out):
+    """Place a window onto the image and cut-out the resulting
+    rectangle.  The window is an axis aligned rectangle opposite corners
+    at *tl* and *br* (each being an (x,y) pair). *inp* specifies the
+    input file which should be a PNG image.
+    """
+
+    import png
+
+    r = png.Reader(file=inp)
+    x,y,pixels,meta = r.asDirect()
+    if not (0 <= tl[0] < br[0] <= x):
+        raise NotImplementedError()
+    if not (0 <= tl[1] < br[1] <= y):
+        raise NotImplementedError()
+    # Compute left and right bounds for each row
+    l = tl[0] * meta['planes']
+    r = br[0] * meta['planes']
+    def itercrop():
+        """An iterator to perform the crop."""
+
+        for i,row in enumerate(pixels):
+            if i < tl[1]:
+                continue
+            if i >= br[1]:
+                # Same as "raise StopIteration"
+                return
+            yield row[l:r]
+    meta['size'] = (br[0]-tl[0], br[1]-tl[1])
+    w = png.Writer(**meta)
+    w.write(out, itercrop())
+
+def main(argv=None):
+    import sys
+
+    if argv is None:
+        argv = sys.argv
+    argv = argv[1:]
+
+    tl = (0,0)
+    br = tuple(map(int, argv[:2]))
+    if len(argv) >= 4:
+        tl = br
+        br = tuple(map(int, argv[2:4]))
+    if len(argv) in (2, 4):
+        f = sys.stdin
+    else:
+        f = open(argv[-1], 'rb')
+
+    return window(tl, br, f, sys.stdout)
+
+if __name__ == '__main__':
+    main()
new file mode 100644
--- /dev/null
+++ b/build/pypng/plan9topng.py
@@ -0,0 +1,293 @@
+#!/usr/bin/env python
+# $Rev: 184 $
+# $URL: http://pypng.googlecode.com/svn/trunk/code/plan9topng.py $
+
+# Imported from //depot/prj/plan9topam/master/code/plan9topam.py#4 on
+# 2009-06-15.
+
+"""Command line tool to convert from Plan 9 image format to PNG format.
+
+Plan 9 image format description:
+http://plan9.bell-labs.com/magic/man2html/6/image
+"""
+
+# http://www.python.org/doc/2.3.5/lib/module-itertools.html
+import itertools
+# http://www.python.org/doc/2.3.5/lib/module-re.html
+import re
+# http://www.python.org/doc/2.3.5/lib/module-sys.html
+import sys
+
+def block(s, n):
+    # See http://www.python.org/doc/2.6.2/library/functions.html#zip
+    return zip(*[iter(s)]*n)
+
+def convert(f, output=sys.stdout) :
+  """Convert Plan 9 file to PNG format.  Works with either uncompressed
+  or compressed files.
+  """
+
+  r = f.read(11)
+  if r == 'compressed\n' :
+    png(output, *decompress(f))
+  else :
+    png(output, *glue(f, r))
+
+
+def glue(f, r) :
+  """Return (metadata, stream) pair where `r` is the initial portion of
+  the metadata that has already been read from the stream `f`.
+  """
+
+  r = r + f.read(60-len(r))
+  return (r, f)
+
+def meta(r) :
+  """Convert 60 character string `r`, the metadata from an image file.
+  Returns a 5-tuple (*chan*,*minx*,*miny*,*limx*,*limy*).  5-tuples may
+  settle into lists in transit.
+  
+  As per http://plan9.bell-labs.com/magic/man2html/6/image the metadata
+  comprises 5 words separated by blanks.  As it happens each word starts
+  at an index that is a multiple of 12, but this routine does not care
+  about that."""
+
+  r = r.split()
+  # :todo: raise FormatError
+  assert len(r) == 5
+  r = [r[0]] + map(int, r[1:])
+  return r
+
+def bitdepthof(pixel) :
+    """Return the bitdepth for a Plan9 pixel format string."""
+
+    maxd = 0
+    for c in re.findall(r'[a-z]\d*', pixel) :
+        if c[0] != 'x':
+            maxd = max(maxd, int(c[1:]))
+    return maxd
+
+def maxvalof(pixel):
+  """Return the netpbm MAXVAL for a Plan9 pixel format string."""
+
+  bitdepth = bitdepthof(pixel)
+  return (2**bitdepth)-1
+
+def pixmeta(metadata, f) :
+    """Convert (uncompressed) Plan 9 image file to pair of (*metadata*,
+    *pixels*).  This is intended to be used by PyPNG format.  *metadata*
+    is the metadata returned in a dictionary, *pixels* is an iterator that
+    yields each row in boxed row flat pixel format.
+
+    `f`, the input file, should be cued up to the start of the image data.
+    """
+
+    chan,minx,miny,limx,limy = metadata
+    rows = limy - miny
+    width = limx - minx
+    nchans = len(re.findall('[a-wyz]', chan))
+    alpha = 'a' in chan
+    # Iverson's convention for the win!
+    ncolour = nchans - alpha
+    greyscale = ncolour == 1
+    bitdepth = bitdepthof(chan)
+    maxval = 2**bitdepth - 1
+    # PNG style metadata
+    meta=dict(size=(width,rows), bitdepth=bitdepthof(chan),
+      greyscale=greyscale, alpha=alpha, planes=nchans)
+
+    return itertools.imap(lambda x: itertools.chain(*x),
+      block(unpack(f, rows, width, chan, maxval), width)), meta
+
+def png(out, metadata, f):
+    """Convert to PNG format.  `metadata` should be a Plan9 5-tuple; `f`
+    the input file (see :meth:`pixmeta`).
+    """
+
+    import png
+
+    pixels,meta = pixmeta(metadata, f)
+    p = png.Writer(**meta)
+    p.write(out, pixels)
+
+def spam():
+  """Not really spam, but old PAM code, which is in limbo."""
+
+  if nchans == 3 or nchans == 1 :
+    # PGM (P5) or PPM (P6) format.
+    output.write('P%d\n%d %d %d\n' % (5+(nchans==3), width, rows, maxval))
+  else :
+    # PAM format.
+    output.write("""P7
+WIDTH %d
+HEIGHT %d
+DEPTH %d
+MAXVAL %d
+""" % (width, rows, nchans, maxval))
+
+def unpack(f, rows, width, pixel, maxval) :
+  """Unpack `f` into pixels.  Assumes the pixel format is such that the depth
+  is either a multiple or a divisor of 8.
+  `f` is assumed to be an iterator that returns blocks of input such
+  that each block contains a whole number of pixels.  An iterator is
+  returned that yields each pixel as an n-tuple.  `pixel` describes the
+  pixel format using the Plan9 syntax ("k8", "r8g8b8", and so on).
+  """
+
+  def mask(w) :
+    """An integer, to be used as a mask, with bottom `w` bits set to 1."""
+
+    return (1 << w)-1
+
+  def deblock(f, depth, width) :
+    """A "packer" used to convert multiple bytes into single pixels.
+    `depth` is the pixel depth in bits (>= 8), `width` is the row width in
+    pixels.
+    """
+
+    w = depth // 8
+    i = 0
+    for block in f :
+      for i in range(len(block)//w) :
+        p = block[w*i:w*(i+1)]
+        i += w
+        # Convert p to little-endian integer, x
+        x = 0
+        s = 1 # scale
+        for j in p :
+          x += s * ord(j)
+          s <<= 8
+        yield x
+
+  def bitfunge(f, depth, width) :
+    """A "packer" used to convert single bytes into multiple pixels.
+    Depth is the pixel depth (< 8), width is the row width in pixels.
+    """
+
+    for block in f :
+      col = 0
+      for i in block :
+        x = ord(i)
+        for j in range(8/depth) :
+          yield x >> (8 - depth)
+          col += 1
+          if col == width :
+            # A row-end forces a new byte even if we haven't consumed
+            # all of the current byte.  Effectively rows are bit-padded
+            # to make a whole number of bytes.
+            col = 0
+            break
+          x <<= depth
+
+  # number of bits in each channel
+  chan = map(int, re.findall(r'\d+', pixel))
+  # type of each channel
+  type = re.findall('[a-z]', pixel)
+
+  depth = sum(chan)
+
+  # According to the value of depth pick a "packer" that either gathers
+  # multiple bytes into a single pixel (for depth >= 8) or split bytes
+  # into several pixels (for depth < 8)
+  if depth >= 8 :
+    # 
+    assert depth % 8 == 0
+    packer = deblock
+  else :
+    assert 8 % depth == 0
+    packer = bitfunge
+
+  for x in packer(f, depth, width) :
+    # x is the pixel as an unsigned integer
+    o = []
+    # This is a bit yucky.  Extract each channel from the _most_
+    # significant part of x.
+    for j in range(len(chan)) :
+      v = (x >> (depth - chan[j])) & mask(chan[j])
+      x <<= chan[j]
+      if type[j] != 'x' :
+        # scale to maxval
+        v = v * float(maxval) / mask(chan[j])
+        v = int(v+0.5)
+        o.append(v)
+    yield o
+
+
+def decompress(f) :
+  """Decompress a Plan 9 image file.  Assumes f is already cued past the
+  initial 'compressed\n' string.
+  """
+
+  r = meta(f.read(60))
+  return r, decomprest(f, r[4])
+
+
+def decomprest(f, rows) :
+  """Iterator that decompresses the rest of a file once the metadata
+  have been consumed."""
+
+  row = 0
+  while row < rows :
+    row,o = deblock(f)
+    yield o
+
+
+def deblock(f) :
+  """Decompress a single block from a compressed Plan 9 image file.
+  Each block starts with 2 decimal strings of 12 bytes each.  Yields a
+  sequence of (row, data) pairs where row is the total number of rows
+  processed according to the file format and data is the decompressed
+  data for a set of rows."""
+
+  row = int(f.read(12))
+  size = int(f.read(12))
+  if not (0 <= size <= 6000) :
+    raise 'block has invalid size; not a Plan 9 image file?'
+
+  # Since each block is at most 6000 bytes we may as well read it all in
+  # one go.
+  d = f.read(size)
+  i = 0
+  o = []
+
+  while i < size :
+    x = ord(d[i])
+    i += 1
+    if x & 0x80 :
+      x = (x & 0x7f) + 1
+      lit = d[i:i+x]
+      i += x
+      o.extend(lit)
+      continue
+    # x's high-order bit is 0
+    l = (x >> 2) + 3
+    # Offset is made from bottom 2 bits of x and all 8 bits of next
+    # byte.  http://plan9.bell-labs.com/magic/man2html/6/image doesn't
+    # say whether x's 2 bits are most signiificant or least significant.
+    # But it is clear from inspecting a random file,
+    # http://plan9.bell-labs.com/sources/plan9/sys/games/lib/sokoban/images/cargo.bit
+    # that x's 2 bit are most significant.
+    # 
+    offset = (x & 3) << 8
+    offset |= ord(d[i])
+    i += 1
+    # Note: complement operator neatly maps (0 to 1023) to (-1 to
+    # -1024).  Adding len(o) gives a (non-negative) offset into o from
+    # which to start indexing.
+    offset = ~offset + len(o)
+    if offset < 0 :
+      raise 'byte offset indexes off the begininning of the output buffer; not a Plan 9 image file?'
+    for j in range(l) :
+      o.append(o[offset+j])
+  return row,''.join(o)
+
+def main(argv=None) :
+  if argv is None :
+    argv = sys.argv
+  if len(sys.argv) <= 1 :
+    return convert(sys.stdin)
+  else :
+    return convert(open(argv[1], 'rb'))
+
+if __name__ == '__main__' :
+  sys.exit(main())
new file mode 100644
--- /dev/null
+++ b/build/pypng/png.py
@@ -0,0 +1,3785 @@
+#!/usr/bin/env python
+
+# $URL: http://pypng.googlecode.com/svn/trunk/code/png.py $
+# $Rev: 228 $
+
+# png.py - PNG encoder/decoder in pure Python
+#
+# Copyright (C) 2006 Johann C. Rocholl <johann@browsershots.org>
+# Portions Copyright (C) 2009 David Jones <drj@pobox.com>
+# And probably portions Copyright (C) 2006 Nicko van Someren <nicko@nicko.org>
+#
+# Original concept by Johann C. Rocholl.
+#
+# LICENSE (The MIT License)
+#
+# Permission is hereby granted, free of charge, to any person
+# obtaining a copy of this software and associated documentation files
+# (the "Software"), to deal in the Software without restriction,
+# including without limitation the rights to use, copy, modify, merge,
+# publish, distribute, sublicense, and/or sell copies of the Software,
+# and to permit persons to whom the Software is furnished to do so,
+# subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be
+# included in all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+#
+# Changelog (recent first):
+# 2009-03-11 David: interlaced bit depth < 8 (writing).
+# 2009-03-10 David: interlaced bit depth < 8 (reading).
+# 2009-03-04 David: Flat and Boxed pixel formats.
+# 2009-02-26 David: Palette support (writing).
+# 2009-02-23 David: Bit-depths < 8; better PNM support.
+# 2006-06-17 Nicko: Reworked into a class, faster interlacing.
+# 2006-06-17 Johann: Very simple prototype PNG decoder.
+# 2006-06-17 Nicko: Test suite with various image generators.
+# 2006-06-17 Nicko: Alpha-channel, grey-scale, 16-bit/plane support.
+# 2006-06-15 Johann: Scanline iterator interface for large input files.
+# 2006-06-09 Johann: Very simple prototype PNG encoder.
+
+# Incorporated into Bangai-O Development Tools by drj on 2009-02-11 from
+# http://trac.browsershots.org/browser/trunk/pypng/lib/png.py?rev=2885
+
+# Incorporated into pypng by drj on 2009-03-12 from
+# //depot/prj/bangaio/master/code/png.py#67
+
+
+"""
+Pure Python PNG Reader/Writer
+
+This Python module implements support for PNG images (see PNG
+specification at http://www.w3.org/TR/2003/REC-PNG-20031110/ ). It reads
+and writes PNG files with all allowable bit depths (1/2/4/8/16/24/32/48/64
+bits per pixel) and colour combinations: greyscale (1/2/4/8/16 bit); RGB,
+RGBA, LA (greyscale with alpha) with 8/16 bits per channel; colour mapped
+images (1/2/4/8 bit).  Adam7 interlacing is supported for reading and
+writing.  A number of optional chunks can be specified (when writing)
+and understood (when reading): ``tRNS``, ``bKGD``, ``gAMA``.
+
+For help, type ``import png; help(png)`` in your python interpreter.
+
+A good place to start is the :class:`Reader` and :class:`Writer` classes.
+
+Requires Python 2.3.  Limited support is available for Python 2.2, but
+not everything works.  Best with Python 2.4 and higher.  Installation is
+trivial, but see the ``README.txt`` file (with the source distribution)
+for details.
+
+This file can also be used as a command-line utility to convert
+`Netpbm <http://netpbm.sourceforge.net/>`_ PNM files to PNG, and the reverse conversion from PNG to
+PNM. The interface is similar to that of the ``pnmtopng`` program from
+Netpbm.  Type ``python png.py --help`` at the shell prompt
+for usage and a list of options.
+
+A note on spelling and terminology
+----------------------------------
+
+Generally British English spelling is used in the documentation.  So
+that's "greyscale" and "colour".  This not only matches the author's
+native language, it's also used by the PNG specification.
+
+The major colour models supported by PNG (and hence by PyPNG) are:
+greyscale, RGB, greyscale--alpha, RGB--alpha.  These are sometimes
+referred to using the abbreviations: L, RGB, LA, RGBA.  In this case
+each letter abbreviates a single channel: *L* is for Luminance or Luma or
+Lightness which is the channel used in greyscale images; *R*, *G*, *B* stand
+for Red, Green, Blue, the components of a colour image; *A* stands for
+Alpha, the opacity channel (used for transparency effects, but higher
+values are more opaque, so it makes sense to call it opacity).
+
+A note on formats
+-----------------
+
+When getting pixel data out of this module (reading) and presenting
+data to this module (writing) there are a number of ways the data could
+be represented as a Python value.  Generally this module uses one of
+three formats called "flat row flat pixel", "boxed row flat pixel", and
+"boxed row boxed pixel".  Basically the concern is whether each pixel
+and each row comes in its own little tuple (box), or not.
+
+Consider an image that is 3 pixels wide by 2 pixels high, and each pixel
+has RGB components:
+
+Boxed row flat pixel::
+
+  list([R,G,B, R,G,B, R,G,B],
+       [R,G,B, R,G,B, R,G,B])
+
+Each row appears as its own list, but the pixels are flattened so that
+three values for one pixel simply follow the three values for the previous
+pixel.  This is the most common format used, because it provides a good
+compromise between space and convenience.  PyPNG regards itself as
+at liberty to replace any sequence type with any sufficiently compatible
+other sequence type; in practice each row is an array (from the array
+module), and the outer list is sometimes an iterator rather than an
+explicit list (so that streaming is possible).
+
+Flat row flat pixel::
+
+  [R,G,B, R,G,B, R,G,B,
+   R,G,B, R,G,B, R,G,B]
+
+The entire image is one single giant sequence of colour values.
+Generally an array will be used (to save space), not a list.
+
+Boxed row boxed pixel::
+
+  list([ (R,G,B), (R,G,B), (R,G,B) ],
+       [ (R,G,B), (R,G,B), (R,G,B) ])
+
+Each row appears in its own list, but each pixel also appears in its own
+tuple.  A serious memory burn in Python.
+
+In all cases the top row comes first, and for each row the pixels are
+ordered from left-to-right.  Within a pixel the values appear in the
+order, R-G-B-A (or L-A for greyscale--alpha).
+
+There is a fourth format, mentioned because it is used internally,
+is close to what lies inside a PNG file itself, and has some support
+from the public API.  This format is called packed.  When packed,
+each row is a sequence of bytes (integers from 0 to 255), just as
+it is before PNG scanline filtering is applied.  When the bit depth
+is 8 this is essentially the same as boxed row flat pixel; when the
+bit depth is less than 8, several pixels are packed into each byte;
+when the bit depth is 16 (the only value more than 8 that is supported
+by the PNG image format) each pixel value is decomposed into 2 bytes
+(and `packed` is a misnomer).  This format is used by the
+:meth:`Writer.write_packed` method.  It isn't usually a convenient
+format, but may be just right if the source data for the PNG image
+comes from something that uses a similar format (for example, 1-bit
+BMPs, or another PNG file).
+
+And now, my famous members
+--------------------------
+"""
+
+# http://www.python.org/doc/2.2.3/whatsnew/node5.html
+from __future__ import generators
+
+__version__ = "$URL: http://pypng.googlecode.com/svn/trunk/code/png.py $ $Rev: 228 $"
+
+from array import array
+try: # See :pyver:old
+    import itertools
+except:
+    pass
+import math
+# http://www.python.org/doc/2.4.4/lib/module-operator.html
+import operator
+import struct
+import sys
+import zlib
+# http://www.python.org/doc/2.4.4/lib/module-warnings.html
+import warnings
+
+
+__all__ = ['Image', 'Reader', 'Writer', 'write_chunks', 'from_array']
+
+
+# The PNG signature.
+# http://www.w3.org/TR/PNG/#5PNG-file-signature
+_signature = struct.pack('8B', 137, 80, 78, 71, 13, 10, 26, 10)
+
+_adam7 = ((0, 0, 8, 8),
+          (4, 0, 8, 8),
+          (0, 4, 4, 8),
+          (2, 0, 4, 4),
+          (0, 2, 2, 4),
+          (1, 0, 2, 2),
+          (0, 1, 1, 2))
+
+def group(s, n):
+    # See
+    # http://www.python.org/doc/2.6/library/functions.html#zip
+    return zip(*[iter(s)]*n)
+
+def isarray(x):
+    """Same as ``isinstance(x, array)`` except on Python 2.2, where it
+    always returns ``False``.  This helps PyPNG work on Python 2.2.
+    """
+
+    try:
+        return isinstance(x, array)
+    except:
+        return False
+
+try:  # see :pyver:old
+    array.tostring
+except:
+    def tostring(row):
+        l = len(row)
+        return struct.pack('%dB' % l, *row)
+else:
+    def tostring(row):
+        """Convert row of bytes to string.  Expects `row` to be an
+        ``array``.
+        """
+        return row.tostring()
+
+# Conditionally convert to bytes.  Works on Python 2 and Python 3.
+try:
+    bytes('', 'ascii')
+    def strtobytes(x): return bytes(x, 'iso8859-1')
+    def bytestostr(x): return str(x, 'iso8859-1')
+except:
+    strtobytes = str
+    bytestostr = str
+
+def interleave_planes(ipixels, apixels, ipsize, apsize):
+    """
+    Interleave (colour) planes, e.g. RGB + A = RGBA.
+
+    Return an array of pixels consisting of the `ipsize` elements of data
+    from each pixel in `ipixels` followed by the `apsize` elements of data
+    from each pixel in `apixels`.  Conventionally `ipixels` and
+    `apixels` are byte arrays so the sizes are bytes, but it actually
+    works with any arrays of the same type.  The returned array is the
+    same type as the input arrays which should be the same type as each other.
+    """
+
+    itotal = len(ipixels)
+    atotal = len(apixels)
+    newtotal = itotal + atotal
+    newpsize = ipsize + apsize
+    # Set up the output buffer
+    # See http://www.python.org/doc/2.4.4/lib/module-array.html#l2h-1356
+    out = array(ipixels.typecode)
+    # It's annoying that there is no cheap way to set the array size :-(
+    out.extend(ipixels)
+    out.extend(apixels)
+    # Interleave in the pixel data
+    for i in range(ipsize):
+        out[i:newtotal:newpsize] = ipixels[i:itotal:ipsize]
+    for i in range(apsize):
+        out[i+ipsize:newtotal:newpsize] = apixels[i:atotal:apsize]
+    return out
+
+def check_palette(palette):
+    """Check a palette argument (to the :class:`Writer` class) for validity.
+    Returns the palette as a list if okay; raises an exception otherwise.
+    """
+
+    # None is the default and is allowed.
+    if palette is None:
+        return None
+
+    p = list(palette)
+    if not (0 < len(p) <= 256):
+        raise ValueError("a palette must have between 1 and 256 entries")
+    seen_triple = False
+    for i,t in enumerate(p):
+        if len(t) not in (3,4):
+            raise ValueError(
+              "palette entry %d: entries must be 3- or 4-tuples." % i)
+        if len(t) == 3:
+            seen_triple = True
+        if seen_triple and len(t) == 4:
+            raise ValueError(
+              "palette entry %d: all 4-tuples must precede all 3-tuples" % i)
+        for x in t:
+            if int(x) != x or not(0 <= x <= 255):
+                raise ValueError(
+                  "palette entry %d: values must be integer: 0 <= x <= 255" % i)
+    return p
+
+class Error(Exception):
+    prefix = 'Error'
+    def __str__(self):
+        return self.prefix + ': ' + ' '.join(self.args)
+
+class FormatError(Error):
+    """Problem with input file format.  In other words, PNG file does
+    not conform to the specification in some way and is invalid.
+    """
+
+    prefix = 'FormatError'
+
+class ChunkError(FormatError):
+    prefix = 'ChunkError'
+
+
+class Writer:
+    """
+    PNG encoder in pure Python.
+    """
+
+    def __init__(self, width=None, height=None,
+                 size=None,
+                 greyscale=False,
+                 alpha=False,
+                 bitdepth=8,
+                 palette=None,
+                 transparent=None,
+                 background=None,
+                 gamma=None,
+                 compression=None,
+                 interlace=False,
+                 bytes_per_sample=None, # deprecated
+                 planes=None,
+                 colormap=None,
+                 maxval=None,
+                 chunk_limit=2**20):
+        """
+        Create a PNG encoder object.
+
+        Arguments:
+
+        width, height
+          Image size in pixels, as two separate arguments.
+        size
+          Image size (w,h) in pixels, as single argument.
+        greyscale
+          Input data is greyscale, not RGB.
+        alpha
+          Input data has alpha channel (RGBA or LA).
+        bitdepth
+          Bit depth: from 1 to 16.
+        palette
+          Create a palette for a colour mapped image (colour type 3).
+        transparent
+          Specify a transparent colour (create a ``tRNS`` chunk).
+        background
+          Specify a default background colour (create a ``bKGD`` chunk).
+        gamma
+          Specify a gamma value (create a ``gAMA`` chunk).
+        compression
+          zlib compression level (1-9).
+        interlace
+          Create an interlaced image.
+        chunk_limit
+          Write multiple ``IDAT`` chunks to save memory.
+
+        The image size (in pixels) can be specified either by using the
+        `width` and `height` arguments, or with the single `size`
+        argument.  If `size` is used it should be a pair (*width*,
+        *height*).
+
+        `greyscale` and `alpha` are booleans that specify whether
+        an image is greyscale (or colour), and whether it has an
+        alpha channel (or not).
+
+        `bitdepth` specifies the bit depth of the source pixel values.
+        Each source pixel value must be an integer between 0 and
+        ``2**bitdepth-1``.  For example, 8-bit images have values
+        between 0 and 255.  PNG only stores images with bit depths of
+        1,2,4,8, or 16.  When `bitdepth` is not one of these values,
+        the next highest valid bit depth is selected, and an ``sBIT``
+        (significant bits) chunk is generated that specifies the original
+        precision of the source image.  In this case the supplied pixel
+        values will be rescaled to fit the range of the selected bit depth.
+
+        The details of which bit depth / colour model combinations the
+        PNG file format supports directly, are somewhat arcane
+        (refer to the PNG specification for full details).  Briefly:
+        "small" bit depths (1,2,4) are only allowed with greyscale and
+        colour mapped images; colour mapped images cannot have bit depth
+        16.
+
+        For colour mapped images (in other words, when the `palette`
+        argument is specified) the `bitdepth` argument must match one of
+        the valid PNG bit depths: 1, 2, 4, or 8.  (It is valid to have a
+        PNG image with a palette and an ``sBIT`` chunk, but the meaning
+        is slightly different; it would be awkward to press the
+        `bitdepth` argument into service for this.)
+
+        The `palette` option, when specified, causes a colour mapped image
+        to be created: the PNG colour type is set to 3; greyscale
+        must not be set; alpha must not be set; transparent must
+        not be set; the bit depth must be 1,2,4, or 8.  When a colour
+        mapped image is created, the pixel values are palette indexes
+        and the `bitdepth` argument specifies the size of these indexes
+        (not the size of the colour values in the palette).
+
+        The palette argument value should be a sequence of 3- or
+        4-tuples.  3-tuples specify RGB palette entries; 4-tuples
+        specify RGBA palette entries.  If both 4-tuples and 3-tuples
+        appear in the sequence then all the 4-tuples must come
+        before all the 3-tuples.  A ``PLTE`` chunk is created; if there
+        are 4-tuples then a ``tRNS`` chunk is created as well.  The
+        ``PLTE`` chunk will contain all the RGB triples in the same
+        sequence; the ``tRNS`` chunk will contain the alpha channel for
+        all the 4-tuples, in the same sequence.  Palette entries
+        are always 8-bit.
+
+        If specified, the `transparent` and `background` parameters must
+        be a tuple with three integer values for red, green, blue, or
+        a simple integer (or singleton tuple) for a greyscale image.
+
+        If specified, the `gamma` parameter must be a positive number
+        (generally, a float).  A ``gAMA`` chunk will be created.  Note that
+        this will not change the values of the pixels as they appear in
+        the PNG file, they are assumed to have already been converted
+        appropriately for the gamma specified.
+
+        The `compression` argument specifies the compression level
+        to be used by the ``zlib`` module.  Higher values are likely
+        to compress better, but will be slower to compress.  The
+        default for this argument is ``None``; this does not mean
+        no compression, rather it means that the default from the
+        ``zlib`` module is used (which is generally acceptable).
+
+        If `interlace` is true then an interlaced image is created
+        (using PNG's so far only interace method, *Adam7*).  This does not
+        affect how the pixels should be presented to the encoder, rather
+        it changes how they are arranged into the PNG file.  On slow
+        connexions interlaced images can be partially decoded by the
+        browser to give a rough view of the image that is successively
+        refined as more image data appears.
+        
+        .. note ::
+        
+          Enabling the `interlace` option requires the entire image
+          to be processed in working memory.
+
+        `chunk_limit` is used to limit the amount of memory used whilst
+        compressing the image.  In order to avoid using large amounts of
+        memory, multiple ``IDAT`` chunks may be created.
+        """
+
+        # At the moment the `planes` argument is ignored;
+        # its purpose is to act as a dummy so that
+        # ``Writer(x, y, **info)`` works, where `info` is a dictionary
+        # returned by Reader.read and friends.
+        # Ditto for `colormap`.
+
+        # A couple of helper functions come first.  Best skipped if you
+        # are reading through.
+
+        def isinteger(x):
+            try:
+                return int(x) == x
+            except:
+                return False
+
+        def check_color(c, which):
+            """Checks that a colour argument for transparent or
+            background options is the right form.  Also "corrects" bare
+            integers to 1-tuples.
+            """
+
+            if c is None:
+                return c
+            if greyscale:
+                try:
+                    l = len(c)
+                except TypeError:
+                    c = (c,)
+                if len(c) != 1:
+                    raise ValueError("%s for greyscale must be 1-tuple" %
+                        which)
+                if not isinteger(c[0]):
+                    raise ValueError(
+                        "%s colour for greyscale must be integer" %
+                        which)
+            else:
+                if not (len(c) == 3 and
+                        isinteger(c[0]) and
+                        isinteger(c[1]) and
+                        isinteger(c[2])):
+                    raise ValueError(
+                        "%s colour must be a triple of integers" %
+                        which)
+            return c
+
+        if size:
+            if len(size) != 2:
+                raise ValueError(
+                  "size argument should be a pair (width, height)")
+            if width is not None and width != size[0]:
+                raise ValueError(
+                  "size[0] (%r) and width (%r) should match when both are used."
+                    % (size[0], width))
+            if height is not None and height != size[1]:
+                raise ValueError(
+                  "size[1] (%r) and height (%r) should match when both are used."
+                    % (size[1], height))
+            width,height = size
+        del size
+
+        if width <= 0 or height <= 0:
+            raise ValueError("width and height must be greater than zero")
+        if not isinteger(width) or not isinteger(height):
+            raise ValueError("width and height must be integers")
+        # http://www.w3.org/TR/PNG/#7Integers-and-byte-order
+        if width > 2**32-1 or height > 2**32-1:
+            raise ValueError("width and height cannot exceed 2**32-1")
+
+        if alpha and transparent is not None:
+            raise ValueError(
+                "transparent colour not allowed with alpha channel")
+
+        if bytes_per_sample is not None:
+            warnings.warn('please use bitdepth instead of bytes_per_sample',
+                          DeprecationWarning)
+            if bytes_per_sample not in (0.125, 0.25, 0.5, 1, 2):
+                raise ValueError(
+                    "bytes per sample must be .125, .25, .5, 1, or 2")
+            bitdepth = int(8*bytes_per_sample)
+        del bytes_per_sample
+        if not isinteger(bitdepth) or bitdepth < 1 or 16 < bitdepth:
+            raise ValueError("bitdepth (%r) must be a postive integer <= 16" %
+              bitdepth)
+
+        self.rescale = None
+        if palette:
+            if bitdepth not in (1,2,4,8):
+                raise ValueError("with palette, bitdepth must be 1, 2, 4, or 8")
+            if transparent is not None:
+                raise ValueError("transparent and palette not compatible")
+            if alpha:
+                raise ValueError("alpha and palette not compatible")
+            if greyscale:
+                raise ValueError("greyscale and palette not compatible")
+        else:
+            # No palette, check for sBIT chunk generation.
+            if alpha or not greyscale:
+                if bitdepth not in (8,16):
+                    targetbitdepth = (8,16)[bitdepth > 8]
+                    self.rescale = (bitdepth, targetbitdepth)
+                    bitdepth = targetbitdepth
+                    del targetbitdepth
+            else:
+                assert greyscale
+                assert not alpha
+                if bitdepth not in (1,2,4,8,16):
+                    if bitdepth > 8:
+                        targetbitdepth = 16
+                    elif bitdepth == 3:
+                        targetbitdepth = 4
+                    else:
+                        assert bitdepth in (5,6,7)
+                        targetbitdepth = 8
+                    self.rescale = (bitdepth, targetbitdepth)
+                    bitdepth = targetbitdepth
+                    del targetbitdepth
+
+        if bitdepth < 8 and (alpha or not greyscale and not palette):
+            raise ValueError(
+              "bitdepth < 8 only permitted with greyscale or palette")
+        if bitdepth > 8 and palette:
+            raise ValueError(
+                "bit depth must be 8 or less for images with palette")
+
+        transparent = check_color(transparent, 'transparent')
+        background = check_color(background, 'background')
+
+        # It's important that the true boolean values (greyscale, alpha,
+        # colormap, interlace) are converted to bool because Iverson's
+        # convention is relied upon later on.
+        self.width = width
+        self.height = height
+        self.transparent = transparent
+        self.background = background
+        self.gamma = gamma
+        self.greyscale = bool(greyscale)
+        self.alpha = bool(alpha)
+        self.colormap = bool(palette)
+        self.bitdepth = int(bitdepth)
+        self.compression = compression
+        self.chunk_limit = chunk_limit
+        self.interlace = bool(interlace)
+        self.palette = check_palette(palette)
+
+        self.color_type = 4*self.alpha + 2*(not greyscale) + 1*self.colormap
+        assert self.color_type in (0,2,3,4,6)
+
+        self.color_planes = (3,1)[self.greyscale or self.colormap]
+        self.planes = self.color_planes + self.alpha
+        # :todo: fix for bitdepth < 8
+        self.psize = (self.bitdepth/8) * self.planes
+
+    def make_palette(self):
+        """Create the byte sequences for a ``PLTE`` and if necessary a
+        ``tRNS`` chunk.  Returned as a pair (*p*, *t*).  *t* will be
+        ``None`` if no ``tRNS`` chunk is necessary.
+        """
+
+        p = array('B')
+        t = array('B')
+
+        for x in self.palette:
+            p.extend(x[0:3])
+            if len(x) > 3:
+                t.append(x[3])
+        p = tostring(p)
+        t = tostring(t)
+        if t:
+            return p,t
+        return p,None
+
+    def write(self, outfile, rows):
+        """Write a PNG image to the output file.  `rows` should be
+        an iterable that yields each row in boxed row flat pixel format.
+        The rows should be the rows of the original image, so there
+        should be ``self.height`` rows of ``self.width * self.planes`` values.
+        If `interlace` is specified (when creating the instance), then
+        an interlaced PNG file will be written.  Supply the rows in the
+        normal image order; the interlacing is carried out internally.
+        
+        .. note ::
+
+          Interlacing will require the entire image to be in working memory.
+        """
+
+        if self.interlace:
+            fmt = 'BH'[self.bitdepth > 8]
+            a = array(fmt, itertools.chain(*rows))
+            return self.write_array(outfile, a)
+        else:
+            nrows = self.write_passes(outfile, rows)
+            if nrows != self.height:
+                raise ValueError(
+                  "rows supplied (%d) does not match height (%d)" %
+                  (nrows, self.height))
+
+    def write_passes(self, outfile, rows, packed=False):
+        """
+        Write a PNG image to the output file.
+
+        Most users are expected to find the :meth:`write` or
+        :meth:`write_array` method more convenient.
+        
+        The rows should be given to this method in the order that
+        they appear in the output file.  For straightlaced images,
+        this is the usual top to bottom ordering, but for interlaced
+        images the rows should have already been interlaced before
+        passing them to this function.
+
+        `rows` should be an iterable that yields each row.  When
+        `packed` is ``False`` the rows should be in boxed row flat pixel
+        format; when `packed` is ``True`` each row should be a packed
+        sequence of bytes.
+
+        """
+
+        # http://www.w3.org/TR/PNG/#5PNG-file-signature
+        outfile.write(_signature)
+
+        # http://www.w3.org/TR/PNG/#11IHDR
+        write_chunk(outfile, 'IHDR',
+                    struct.pack("!2I5B", self.width, self.height,
+                                self.bitdepth, self.color_type,
+                                0, 0, self.interlace))
+
+        # See :chunk:order
+        # http://www.w3.org/TR/PNG/#11gAMA
+        if self.gamma is not None:
+            write_chunk(outfile, 'gAMA',
+                        struct.pack("!L", int(round(self.gamma*1e5))))
+
+        # See :chunk:order
+        # http://www.w3.org/TR/PNG/#11sBIT
+        if self.rescale:
+            write_chunk(outfile, 'sBIT',
+                struct.pack('%dB' % self.planes,
+                            *[self.rescale[0]]*self.planes))
+        
+        # :chunk:order: Without a palette (PLTE chunk), ordering is
+        # relatively relaxed.  With one, gAMA chunk must precede PLTE
+        # chunk which must precede tRNS and bKGD.
+        # See http://www.w3.org/TR/PNG/#5ChunkOrdering
+        if self.palette:
+            p,t = self.make_palette()
+            write_chunk(outfile, 'PLTE', p)
+            if t:
+                # tRNS chunk is optional.  Only needed if palette entries
+                # have alpha.
+                write_chunk(outfile, 'tRNS', t)
+
+        # http://www.w3.org/TR/PNG/#11tRNS
+        if self.transparent is not None:
+            if self.greyscale:
+                write_chunk(outfile, 'tRNS',
+                            struct.pack("!1H", *self.transparent))
+            else:
+                write_chunk(outfile, 'tRNS',
+                            struct.pack("!3H", *self.transparent))
+
+        # http://www.w3.org/TR/PNG/#11bKGD
+        if self.background is not None:
+            if self.greyscale:
+                write_chunk(outfile, 'bKGD',
+                            struct.pack("!1H", *self.background))
+            else:
+                write_chunk(outfile, 'bKGD',
+                            struct.pack("!3H", *self.background))
+
+        # http://www.w3.org/TR/PNG/#11IDAT
+        if self.compression is not None:
+            compressor = zlib.compressobj(self.compression)
+        else:
+            compressor = zlib.compressobj()
+
+        # Choose an extend function based on the bitdepth.  The extend
+        # function packs/decomposes the pixel values into bytes and
+        # stuffs them onto the data array.
+        data = array('B')
+        if self.bitdepth == 8 or packed:
+            extend = data.extend
+        elif self.bitdepth == 16:
+            # Decompose into bytes
+            def extend(sl):
+                fmt = '!%dH' % len(sl)
+                data.extend(array('B', struct.pack(fmt, *sl)))
+        else:
+            # Pack into bytes
+            assert self.bitdepth < 8
+            # samples per byte
+            spb = int(8/self.bitdepth)
+            def extend(sl):
+                a = array('B', sl)
+                # Adding padding bytes so we can group into a whole
+                # number of spb-tuples.
+                l = float(len(a))
+                extra = math.ceil(l / float(spb))*spb - l
+                a.extend([0]*int(extra))
+                # Pack into bytes
+                l = group(a, spb)
+                l = map(lambda e: reduce(lambda x,y:
+                                           (x << self.bitdepth) + y, e), l)
+                data.extend(l)
+        if self.rescale:
+            oldextend = extend
+            factor = \
+              float(2**self.rescale[1]-1) / float(2**self.rescale[0]-1)
+            def extend(sl):
+                oldextend(map(lambda x: int(round(factor*x)), sl))
+
+        # Build the first row, testing mostly to see if we need to
+        # changed the extend function to cope with NumPy integer types
+        # (they cause our ordinary definition of extend to fail, so we
+        # wrap it).  See
+        # http://code.google.com/p/pypng/issues/detail?id=44
+        enumrows = enumerate(rows)
+        del rows
+
+        # First row's filter type.
+        data.append(0)
+        # :todo: Certain exceptions in the call to ``.next()`` or the
+        # following try would indicate no row data supplied.
+        # Should catch.
+        i,row = enumrows.next()
+        try:
+            # If this fails...
+            extend(row)
+        except:
+            # ... try a version that converts the values to int first.
+            # Not only does this work for the (slightly broken) NumPy
+            # types, there are probably lots of other, unknown, "nearly"
+            # int types it works for.
+            def wrapmapint(f):
+                return lambda sl: f(map(int, sl))
+            extend = wrapmapint(extend)
+            del wrapmapint
+            extend(row)
+
+        for i,row in enumrows:
+            # Add "None" filter type.  Currently, it's essential that
+            # this filter type be used for every scanline as we do not
+            # mark the first row of a reduced pass image; that means we
+            # could accidentally compute the wrong filtered scanline if
+            # we used "up", "average", or "paeth" on such a line.
+            data.append(0)
+            extend(row)
+            if len(data) > self.chunk_limit:
+                compressed = compressor.compress(tostring(data))
+                if len(compressed):
+                    # print >> sys.stderr, len(data), len(compressed)
+                    write_chunk(outfile, 'IDAT', compressed)
+                # Because of our very witty definition of ``extend``,
+                # above, we must re-use the same ``data`` object.  Hence
+                # we use ``del`` to empty this one, rather than create a
+                # fresh one (which would be my natural FP instinct).
+                del data[:]
+        if len(data):
+            compressed = compressor.compress(tostring(data))
+        else:
+            compressed = ''
+        flushed = compressor.flush()
+        if len(compressed) or len(flushed):
+            # print >> sys.stderr, len(data), len(compressed), len(flushed)
+            write_chunk(outfile, 'IDAT', compressed + flushed)
+        # http://www.w3.org/TR/PNG/#11IEND
+        write_chunk(outfile, 'IEND')
+        return i+1
+
+    def write_array(self, outfile, pixels):
+        """
+        Write an array in flat row flat pixel format as a PNG file on
+        the output file.  See also :meth:`write` method.
+        """
+
+        if self.interlace:
+            self.write_passes(outfile, self.array_scanlines_interlace(pixels))
+        else:
+            self.write_passes(outfile, self.array_scanlines(pixels))
+
+    def write_packed(self, outfile, rows):
+        """
+        Write PNG file to `outfile`.  The pixel data comes from `rows`
+        which should be in boxed row packed format.  Each row should be
+        a sequence of packed bytes.
+
+        Technically, this method does work for interlaced images but it
+        is best avoided.  For interlaced images, the rows should be
+        presented in the order that they appear in the file.
+
+        This method should not be used when the source image bit depth
+        is not one naturally supported by PNG; the bit depth should be
+        1, 2, 4, 8, or 16.
+        """
+
+        if self.rescale:
+            raise Error("write_packed method not suitable for bit depth %d" %
+              self.rescale[0])
+        return self.write_passes(outfile, rows, packed=True)
+
+    def convert_pnm(self, infile, outfile):
+        """
+        Convert a PNM file containing raw pixel data into a PNG file
+        with the parameters set in the writer object.  Works for
+        (binary) PGM, PPM, and PAM formats.
+        """
+
+        if self.interlace:
+            pixels = array('B')
+            pixels.fromfile(infile,
+                            (self.bitdepth/8) * self.color_planes *
+                            self.width * self.height)
+            self.write_passes(outfile, self.array_scanlines_interlace(pixels))
+        else:
+            self.write_passes(outfile, self.file_scanlines(infile))
+
+    def convert_ppm_and_pgm(self, ppmfile, pgmfile, outfile):
+        """
+        Convert a PPM and PGM file containing raw pixel data into a
+        PNG outfile with the parameters set in the writer object.
+        """
+        pixels = array('B')
+        pixels.fromfile(ppmfile,
+                        (self.bitdepth/8) * self.color_planes *
+                        self.width * self.height)
+        apixels = array('B')
+        apixels.fromfile(pgmfile,
+                         (self.bitdepth/8) *
+                         self.width * self.height)
+        pixels = interleave_planes(pixels, apixels,
+                                   (self.bitdepth/8) * self.color_planes,
+                                   (self.bitdepth/8))
+        if self.interlace:
+            self.write_passes(outfile, self.array_scanlines_interlace(pixels))
+        else:
+            self.write_passes(outfile, self.array_scanlines(pixels))
+
+    def file_scanlines(self, infile):
+        """
+        Generates boxed rows in flat pixel format, from the input file
+        `infile`.  It assumes that the input file is in a "Netpbm-like"
+        binary format, and is positioned at the beginning of the first
+        pixel.  The number of pixels to read is taken from the image
+        dimensions (`width`, `height`, `planes`) and the number of bytes
+        per value is implied by the image `bitdepth`.
+        """
+
+        # Values per row
+        vpr = self.width * self.planes
+        row_bytes = vpr
+        if self.bitdepth > 8:
+            assert self.bitdepth == 16
+            row_bytes *= 2
+            fmt = '>%dH' % vpr
+            def line():
+                return array('H', struct.unpack(fmt, infile.read(row_bytes)))
+        else:
+            def line():
+                scanline = array('B', infile.read(row_bytes))
+                return scanline
+        for y in range(self.height):
+            yield line()
+
+    def array_scanlines(self, pixels):
+        """
+        Generates boxed rows (flat pixels) from flat rows (flat pixels)
+        in an array.
+        """
+
+        # Values per row
+        vpr = self.width * self.planes
+        stop = 0
+        for y in range(self.height):
+            start = stop
+            stop = start + vpr
+            yield pixels[start:stop]
+
+    def array_scanlines_interlace(self, pixels):
+        """
+        Generator for interlaced scanlines from an array.  `pixels` is
+        the full source image in flat row flat pixel format.  The
+        generator yields each scanline of the reduced passes in turn, in
+        boxed row flat pixel format.
+        """
+
+        # http://www.w3.org/TR/PNG/#8InterlaceMethods
+        # Array type.
+        fmt = 'BH'[self.bitdepth > 8]
+        # Value per row
+        vpr = self.width * self.planes
+        for xstart, ystart, xstep, ystep in _adam7:
+            if xstart >= self.width:
+                continue
+            # Pixels per row (of reduced image)
+            ppr = int(math.ceil((self.width-xstart)/float(xstep)))
+            # number of values in reduced image row.
+            row_len = ppr*self.planes
+            for y in range(ystart, self.height, ystep):
+                if xstep == 1:
+                    offset = y * vpr
+                    yield pixels[offset:offset+vpr]
+                else:
+                    row = array(fmt)
+                    # There's no easier way to set the length of an array
+                    row.extend(pixels[0:row_len])
+                    offset = y * vpr + xstart * self.planes
+                    end_offset = (y+1) * vpr
+                    skip = self.planes * xstep
+                    for i in range(self.planes):
+                        row[i::self.planes] = \
+                            pixels[offset+i:end_offset:skip]
+                    yield row
+
+def write_chunk(outfile, tag, data=strtobytes('')):
+    """
+    Write a PNG chunk to the output file, including length and
+    checksum.
+    """
+
+    # http://www.w3.org/TR/PNG/#5Chunk-layout
+    outfile.write(struct.pack("!I", len(data)))
+    tag = strtobytes(tag)
+    outfile.write(tag)
+    outfile.write(data)
+    checksum = zlib.crc32(tag)
+    checksum = zlib.crc32(data, checksum)
+    checksum &= 2**32-1
+    outfile.write(struct.pack("!I", checksum))
+
+def write_chunks(out, chunks):
+    """Create a PNG file by writing out the chunks."""
+
+    out.write(_signature)
+    for chunk in chunks:
+        write_chunk(out, *chunk)
+
+def filter_scanline(type, line, fo, prev=None):
+    """Apply a scanline filter to a scanline.  `type` specifies the
+    filter type (0 to 4); `line` specifies the current (unfiltered)
+    scanline as a sequence of bytes; `prev` specifies the previous
+    (unfiltered) scanline as a sequence of bytes. `fo` specifies the
+    filter offset; normally this is size of a pixel in bytes (the number
+    of bytes per sample times the number of channels), but when this is
+    < 1 (for bit depths < 8) then the filter offset is 1.
+    """
+
+    assert 0 <= type < 5
+
+    # The output array.  Which, pathetically, we extend one-byte at a
+    # time (fortunately this is linear).
+    out = array('B', [type])
+
+    def sub():
+        ai = -fo
+        for x in line:
+            if ai >= 0:
+                x = (x - line[ai]) & 0xff
+            out.append(x)
+            ai += 1
+    def up():
+        for i,x in enumerate(line):
+            x = (x - prev[i]) & 0xff
+            out.append(x)
+    def average():
+        ai = -fo
+        for i,x in enumerate(line):
+            if ai >= 0:
+                x = (x - ((line[ai] + prev[i]) >> 1)) & 0xff
+            else:
+                x = (x - (prev[i] >> 1)) & 0xff
+            out.append(x)
+            ai += 1
+    def paeth():
+        # http://www.w3.org/TR/PNG/#9Filter-type-4-Paeth
+        ai = -fo # also used for ci
+        for i,x in enumerate(line):
+            a = 0
+            b = prev[i]
+            c = 0
+
+            if ai >= 0:
+                a = line[ai]
+                c = prev[ai]
+            p = a + b - c
+            pa = abs(p - a)
+            pb = abs(p - b)
+            pc = abs(p - c)
+            if pa <= pb and pa <= pc: Pr = a
+            elif pb <= pc: Pr = b
+            else: Pr = c
+
+            x = (x - Pr) & 0xff
+            out.append(x)
+            ai += 1
+
+    if not prev:
+        # We're on the first line.  Some of the filters can be reduced
+        # to simpler cases which makes handling the line "off the top"
+        # of the image simpler.  "up" becomes "none"; "paeth" becomes
+        # "left" (non-trivial, but true). "average" needs to be handled
+        # specially.
+        if type == 2: # "up"
+            return line # type = 0
+        elif type == 3:
+            prev = [0]*len(line)
+        elif type == 4: # "paeth"
+            type = 1
+    if type == 0:
+        out.extend(line)
+    elif type == 1:
+        sub()
+    elif type == 2:
+        up()
+    elif type == 3:
+        average()
+    else: # type == 4
+        paeth()
+    return out
+
+
+def from_array(a, mode=None, info={}):
+    """Create a PNG :class:`Image` object from a 2- or 3-dimensional array.
+    One application of this function is easy PIL-style saving:
+    ``png.from_array(pixels, 'L').save('foo.png')``.
+
+    .. note :
+
+      The use of the term *3-dimensional* is for marketing purposes
+      only.  It doesn't actually work.  Please bear with us.  Meanwhile
+      enjoy the complimentary snacks (on request) and please use a
+      2-dimensional array.
+    
+    Unless they are specified using the *info* parameter, the PNG's
+    height and width are taken from the array size.  For a 3 dimensional
+    array the first axis is the height; the second axis is the width;
+    and the third axis is the channel number.  Thus an RGB image that is
+    16 pixels high and 8 wide will use an array that is 16x8x3.  For 2
+    dimensional arrays the first axis is the height, but the second axis
+    is ``width*channels``, so an RGB image that is 16 pixels high and 8
+    wide will use a 2-dimensional array that is 16x24 (each row will be
+    8*3==24 sample values).
+
+    *mode* is a string that specifies the image colour format in a
+    PIL-style mode.  It can be:
+
+    ``'L'``
+      greyscale (1 channel)
+    ``'LA'``
+      greyscale with alpha (2 channel)
+    ``'RGB'``
+      colour image (3 channel)
+    ``'RGBA'``
+      colour image with alpha (4 channel)
+
+    The mode string can also specify the bit depth (overriding how this
+    function normally derives the bit depth, see below).  Appending
+    ``';16'`` to the mode will cause the PNG to be 16 bits per channel;
+    any decimal from 1 to 16 can be used to specify the bit depth.
+
+    When a 2-dimensional array is used *mode* determines how many
+    channels the image has, and so allows the width to be derived from
+    the second array dimension.
+
+    The array is expected to be a ``numpy`` array, but it can be any
+    suitable Python sequence.  For example, a list of lists can be used:
+    ``png.from_array([[0, 255, 0], [255, 0, 255]], 'L')``.  The exact
+    rules are: ``len(a)`` gives the first dimension, height;
+    ``len(a[0])`` gives the second dimension; ``len(a[0][0])`` gives the
+    third dimension, unless an exception is raised in which case a
+    2-dimensional array is assumed.  It's slightly more complicated than
+    that because an iterator of rows can be used, and it all still
+    works.  Using an iterator allows data to be streamed efficiently.
+
+    The bit depth of the PNG is normally taken from the array element's
+    datatype (but if *mode* specifies a bitdepth then that is used
+    instead).  The array element's datatype is determined in a way which
+    is supposed to work both for ``numpy`` arrays and for Python
+    ``array.array`` objects.  A 1 byte datatype will give a bit depth of
+    8, a 2 byte datatype will give a bit depth of 16.  If the datatype
+    does not have an implicit size, for example it is a plain Python
+    list of lists, as above, then a default of 8 is used.
+
+    The *info* parameter is a dictionary that can be used to specify
+    metadata (in the same style as the arguments to the
+    :class:``png.Writer`` class).  For this function the keys that are
+    useful are:
+    
+    height
+      overrides the height derived from the array dimensions and allows
+      *a* to be an iterable.
+    width
+      overrides the width derived from the array dimensions.
+    bitdepth
+      overrides the bit depth derived from the element datatype (but
+      must match *mode* if that also specifies a bit depth).
+
+    Generally anything specified in the
+    *info* dictionary will override any implicit choices that this
+    function would otherwise make, but must match any explicit ones.
+    For example, if the *info* dictionary has a ``greyscale`` key then
+    this must be true when mode is ``'L'`` or ``'LA'`` and false when
+    mode is ``'RGB'`` or ``'RGBA'``.
+    """
+
+    # We abuse the *info* parameter by modifying it.  Take a copy here.
+    # (Also typechecks *info* to some extent).
+    info = dict(info)
+
+    # Syntax check mode string.
+    bitdepth = None
+    try:
+        mode = mode.split(';')
+        if len(mode) not in (1,2):
+            raise Error()
+        if mode[0] not in ('L', 'LA', 'RGB', 'RGBA'):
+            raise Error()
+        if len(mode) == 2:
+            try:
+                bitdepth = int(mode[1])
+            except:
+                raise Error()
+    except Error:
+        raise Error("mode string should be 'RGB' or 'L;16' or similar.")
+    mode = mode[0]
+
+    # Get bitdepth from *mode* if possible.
+    if bitdepth:
+        if info.get('bitdepth') and bitdepth != info['bitdepth']:
+            raise Error("mode bitdepth (%d) should match info bitdepth (%d)." %
+              (bitdepth, info['bitdepth']))
+        info['bitdepth'] = bitdepth
+
+    # Fill in and/or check entries in *info*.
+    # Dimensions.
+    if 'size' in info:
+        # Check width, height, size all match where used.
+        for dimension,axis in [('width', 0), ('height', 1)]:
+            if dimension in info:
+                if info[dimension] != info['size'][axis]:
+                    raise Error(
+                      "info[%r] shhould match info['size'][%r]." %
+                      (dimension, axis))
+        info['width'],info['height'] = info['size']
+    if 'height' not in info:
+        try:
+            l = len(a)
+        except:
+            raise Error(
+              "len(a) does not work, supply info['height'] instead.")
+        info['height'] = l
+    # Colour format.
+    if 'greyscale' in info:
+        if bool(info['greyscale']) != ('L' in mode):
+            raise Error("info['greyscale'] should match mode.")
+    info['greyscale'] = 'L' in mode
+    if 'alpha' in info:
+        if bool(info['alpha']) != ('A' in mode):
+            raise Error("info['alpha'] should match mode.")
+    info['alpha'] = 'A' in mode
+
+    planes = len(mode)
+    if 'planes' in info:
+        if info['planes'] != planes:
+            raise Error("info['planes'] should match mode.")
+
+    # In order to work out whether we the array is 2D or 3D we need its
+    # first row, which requires that we take a copy of its iterator.
+    # We may also need the first row to derive width and bitdepth.
+    a,t = itertools.tee(a)
+    row = t.next()
+    del t
+    try:
+        row[0][0]
+        threed = True
+        testelement = row[0]
+    except:
+        threed = False
+        testelement = row
+    if 'width' not in info:
+        if threed:
+            width = len(row)
+        else:
+            width = len(row) // planes
+        info['width'] = width
+
+    # Not implemented yet
+    assert not threed
+
+    if 'bitdepth' not in info:
+        try:
+            dtype = testelement.dtype
+            # goto the "else:" clause.  Sorry.
+        except:
+            try:
+                # Try a Python array.array.
+                bitdepth = 8 * testelement.itemsize
+            except:
+                # We can't determine it from the array element's
+                # datatype, use a default of 8.
+                bitdepth = 8
+        else:
+            # If we got here without exception, we now assume that
+            # the array is a numpy array.
+            if dtype.kind == 'b':
+                bitdepth = 1
+            else:
+                bitdepth = 8 * dtype.itemsize
+        info['bitdepth'] = bitdepth
+
+    for thing in 'width height bitdepth greyscale alpha'.split():
+        assert thing in info
+    return Image(a, info)
+
+# So that refugee's from PIL feel more at home.  Not documented.
+fromarray = from_array
+
+class Image:
+    """A PNG image.
+    You can create an :class:`Image` object from an array of pixels by calling
+    :meth:`png.from_array`.  It can be saved to disk with the
+    :meth:`save` method."""
+    def __init__(self, rows, info):
+        """
+        .. note ::
+        
+          The constructor is not public.  Please do not call it.
+        """
+        
+        self.rows = rows
+        self.info = info
+
+    def save(self, file):
+        """Save the image to *file*.  If *file* looks like an open file
+        descriptor then it is used, otherwise it is treated as a
+        filename and a fresh file is opened.
+
+        In general, you can only call this method once; after it has
+        been called the first time and the PNG image has been saved, the
+        source data will have been streamed, and cannot be streamed
+        again.
+        """
+
+        w = Writer(**self.info)
+
+        try:
+            file.write
+            def close(): pass
+        except:
+            file = open(file, 'wb')
+            def close(): file.close()
+
+        try:
+            w.write(file, self.rows)
+        finally:
+            close()
+
+class _readable:
+    """
+    A simple file-like interface for strings and arrays.
+    """
+
+    def __init__(self, buf):
+        self.buf = buf
+        self.offset = 0
+
+    def read(self, n):
+        r = self.buf[self.offset:self.offset+n]
+        if isarray(r):
+            r = r.tostring()
+        self.offset += n
+        return r
+
+
+class Reader:
+    """
+    PNG decoder in pure Python.
+    """
+
+    def __init__(self, _guess=None, **kw):
+        """
+        Create a PNG decoder object.
+
+        The constructor expects exactly one keyword argument. If you
+        supply a positional argument instead, it will guess the input
+        type. You can choose among the following keyword arguments:
+
+        filename
+          Name of input file (a PNG file).
+        file
+          A file-like object (object with a read() method).
+        bytes
+          ``array`` or ``string`` with PNG data.
+
+        """
+        if ((_guess is not None and len(kw) != 0) or
+            (_guess is None and len(kw) != 1)):
+            raise TypeError("Reader() takes exactly 1 argument")
+
+        # Will be the first 8 bytes, later on.  See validate_signature.
+        self.signature = None
+        self.transparent = None
+        # A pair of (len,type) if a chunk has been read but its data and
+        # checksum have not (in other words the file position is just
+        # past the 4 bytes that specify the chunk type).  See preamble
+        # method for how this is used.
+        self.atchunk = None
+
+        if _guess is not None:
+            if isarray(_guess):
+                kw["bytes"] = _guess
+            elif isinstance(_guess, str):
+                kw["filename"] = _guess
+            elif isinstance(_guess, file):
+                kw["file"] = _guess
+
+        if "filename" in kw:
+            self.file = open(kw["filename"], "rb")
+        elif "file" in kw:
+            self.file = kw["file"]
+        elif "bytes" in kw:
+            self.file = _readable(kw["bytes"])
+        else:
+            raise TypeError("expecting filename, file or bytes array")
+
+    def chunk(self, seek=None):
+        """
+        Read the next PNG chunk from the input file; returns a
+        (*type*,*data*) tuple.  *type* is the chunk's type as a string
+        (all PNG chunk types are 4 characters long).  *data* is the
+        chunk's data content, as a string.
+
+        If the optional `seek` argument is
+        specified then it will keep reading chunks until it either runs
+        out of file or finds the type specified by the argument.  Note
+        that in general the order of chunks in PNGs is unspecified, so
+        using `seek` can cause you to miss chunks.
+        """
+
+        self.validate_signature()
+
+        while True:
+            # http://www.w3.org/TR/PNG/#5Chunk-layout
+            if not self.atchunk:
+                self.atchunk = self.chunklentype()
+            length,type = self.atchunk
+            self.atchunk = None
+            data = self.file.read(length)
+            if len(data) != length:
+                raise ChunkError('Chunk %s too short for required %i octets.'
+                  % (type, length))
+            checksum = self.file.read(4)
+            if len(checksum) != 4:
+                raise ValueError('Chunk %s too short for checksum.', tag)
+            if seek and type != seek:
+                continue
+            verify = zlib.crc32(strtobytes(type))
+            verify = zlib.crc32(data, verify)
+            # Whether the output from zlib.crc32 is signed or not varies
+            # according to hideous implementation details, see
+            # http://bugs.python.org/issue1202 .
+            # We coerce it to be positive here (in a way which works on
+            # Python 2.3 and older).
+            verify &= 2**32 - 1
+            verify = struct.pack('!I', verify)
+            if checksum != verify:
+                # print repr(checksum)
+                (a, ) = struct.unpack('!I', checksum)
+                (b, ) = struct.unpack('!I', verify)
+                raise ChunkError(
+                  "Checksum error in %s chunk: 0x%08X != 0x%08X." %
+                  (type, a, b))
+            return type, data
+
+    def chunks(self):
+        """Return an iterator that will yield each chunk as a
+        (*chunktype*, *content*) pair.
+        """
+
+        while True:
+            t,v = self.chunk()
+            yield t,v
+            if t == 'IEND':
+                break
+
+    def undo_filter(self, filter_type, scanline, previous):
+        """Undo the filter for a scanline.  `scanline` is a sequence of
+        bytes that does not include the initial filter type byte.
+        `previous` is decoded previous scanline (for straightlaced
+        images this is the previous pixel row, but for interlaced
+        images, it is the previous scanline in the reduced image, which
+        in general is not the previous pixel row in the final image).
+        When there is no previous scanline (the first row of a
+        straightlaced image, or the first row in one of the passes in an
+        interlaced image), then this argument should be ``None``.
+
+        The scanline will have the effects of filtering removed, and the
+        result will be returned as a fresh sequence of bytes.
+        """
+
+        # :todo: Would it be better to update scanline in place?
+
+        # Create the result byte array.  It seems that the best way to
+        # create the array to be the right size is to copy from an
+        # existing sequence.  *sigh*
+        # If we fill the result with scanline, then this allows a
+        # micro-optimisation in the "null" and "sub" cases.
+        result = array('B', scanline)
+
+        if filter_type == 0:
+            # And here, we _rely_ on filling the result with scanline,
+            # above.
+            return result
+
+        if filter_type not in (1,2,3,4):
+            raise FormatError('Invalid PNG Filter Type.'
+              '  See http://www.w3.org/TR/2003/REC-PNG-20031110/#9Filters .')
+
+        # Filter unit.  The stride from one pixel to the corresponding
+        # byte from the previous previous.  Normally this is the pixel
+        # size in bytes, but when this is smaller than 1, the previous
+        # byte is used instead.
+        fu = max(1, self.psize)
+
+        # For the first line of a pass, synthesize a dummy previous
+        # line.  An alternative approach would be to observe that on the
+        # first line 'up' is the same as 'null', 'paeth' is the same
+        # as 'sub', with only 'average' requiring any special case.
+        if not previous:
+            previous = array('B', [0]*len(scanline))
+
+        def sub():
+            """Undo sub filter."""
+
+            ai = 0
+            # Loops starts at index fu.  Observe that the initial part
+            # of the result is already filled in correctly with
+            # scanline.
+            for i in range(fu, len(result)):
+                x = scanline[i]
+                a = result[ai]
+                result[i] = (x + a) & 0xff
+                ai += 1
+
+        def up():
+            """Undo up filter."""
+
+            for i in range(len(result)):
+                x = scanline[i]
+                b = previous[i]
+                result[i] = (x + b) & 0xff
+
+        def average():
+            """Undo average filter."""
+
+            ai = -fu
+            for i in range(len(result)):
+                x = scanline[i]
+                if ai < 0:
+                    a = 0
+                else:
+                    a = result[ai]
+                b = previous[i]
+                result[i] = (x + ((a + b) >> 1)) & 0xff
+                ai += 1
+
+        def paeth():
+            """Undo Paeth filter."""
+
+            # Also used for ci.
+            ai = -fu
+            for i in range(len(result)):
+                x = scanline[i]
+                if ai < 0:
+                    a = c = 0
+                else:
+                    a = result[ai]
+                    c = previous[ai]
+                b = previous[i]
+                p = a + b - c
+                pa = abs(p - a)
+                pb = abs(p - b)
+                pc = abs(p - c)
+                if pa <= pb and pa <= pc:
+                    pr = a
+                elif pb <= pc:
+                    pr = b
+                else:
+                    pr = c
+                result[i] = (x + pr) & 0xff
+                ai += 1
+
+        # Call appropriate filter algorithm.  Note that 0 has already
+        # been dealt with.
+        (None, sub, up, average, paeth)[filter_type]()
+        return result
+
+    def deinterlace(self, raw):
+        """
+        Read raw pixel data, undo filters, deinterlace, and flatten.
+        Return in flat row flat pixel format.
+        """
+
+        # print >> sys.stderr, ("Reading interlaced, w=%s, r=%s, planes=%s," +
+        #     " bpp=%s") % (self.width, self.height, self.planes, self.bps)
+        # Values per row (of the target image)
+        vpr = self.width * self.planes
+
+        # Make a result array, and make it big enough.  Interleaving
+        # writes to the output array randomly (well, not quite), so the
+        # entire output array must be in memory.
+        fmt = 'BH'[self.bitdepth > 8]
+        a = array(fmt, [0]*vpr*self.height)
+        source_offset = 0
+
+        for xstart, ystart, xstep, ystep in _adam7:
+            # print >> sys.stderr, "Adam7: start=%s,%s step=%s,%s" % (
+            #     xstart, ystart, xstep, ystep)
+            if xstart >= self.width:
+                continue
+            # The previous (reconstructed) scanline.  None at the
+            # beginning of a pass to indicate that there is no previous
+            # line.
+            recon = None
+            # Pixels per row (reduced pass image)
+            ppr = int(math.ceil((self.width-xstart)/float(xstep)))
+            # Row size in bytes for this pass.
+            row_size = int(math.ceil(self.psize * ppr))
+            for y in range(ystart, self.height, ystep):
+                filter_type = raw[source_offset]
+                source_offset += 1
+                scanline = raw[source_offset:source_offset+row_size]
+                source_offset += row_size
+                recon = self.undo_filter(filter_type, scanline, recon)
+                # Convert so that there is one element per pixel value
+                flat = self.serialtoflat(recon, ppr)
+                if xstep == 1:
+                    assert xstart == 0
+                    offset = y * vpr
+                    a[offset:offset+vpr] = flat
+                else:
+                    offset = y * vpr + xstart * self.planes
+                    end_offset = (y+1) * vpr
+                    skip = self.planes * xstep
+                    for i in range(self.planes):
+                        a[offset+i:end_offset:skip] = \
+                            flat[i::self.planes]
+        return a
+
+    def iterboxed(self, rows):
+        """Iterator that yields each scanline in boxed row flat pixel
+        format.  `rows` should be an iterator that yields the bytes of
+        each row in turn.
+        """
+
+        def asvalues(raw):
+            """Convert a row of raw bytes into a flat row.  Result may
+            or may not share with argument"""
+
+            if self.bitdepth == 8:
+                return raw
+            if self.bitdepth == 16:
+                raw = tostring(raw)
+                return array('H', struct.unpack('!%dH' % (len(raw)//2), raw))
+            assert self.bitdepth < 8
+            width = self.width
+            # Samples per byte
+            spb = 8//self.bitdepth
+            out = array('B')
+            mask = 2**self.bitdepth - 1
+            shifts = map(self.bitdepth.__mul__, reversed(range(spb)))
+            for o in raw:
+                out.extend(map(lambda i: mask&(o>>i), shifts))
+            return out[:width]
+
+        return itertools.imap(asvalues, rows)
+
+    def serialtoflat(self, bytes, width=None):
+        """Convert serial format (byte stream) pixel data to flat row
+        flat pixel.
+        """
+
+        if self.bitdepth == 8:
+            return bytes
+        if self.bitdepth == 16:
+            bytes = tostring(bytes)
+            return array('H',
+              struct.unpack('!%dH' % (len(bytes)//2), bytes))
+        assert self.bitdepth < 8
+        if width is None:
+            width = self.width
+        # Samples per byte
+        spb = 8//self.bitdepth
+        out = array('B')
+        mask = 2**self.bitdepth - 1
+        shifts = map(self.bitdepth.__mul__, reversed(range(spb)))
+        l = width
+        for o in bytes:
+            out.extend([(mask&(o>>s)) for s in shifts][:l])
+            l -= spb
+            if l <= 0:
+                l = width
+        return out
+
+    def iterstraight(self, raw):
+        """Iterator that undoes the effect of filtering, and yields each
+        row in serialised format (as a sequence of bytes).  Assumes input
+        is straightlaced.  `raw` should be an iterable that yields the
+        raw bytes in chunks of arbitrary size."""
+
+        # length of row, in bytes
+        rb = self.row_bytes
+        a = array('B')
+        # The previous (reconstructed) scanline.  None indicates first
+        # line of image.
+        recon = None
+        for some in raw:
+            a.extend(some)
+            while len(a) >= rb + 1:
+                filter_type = a[0]
+                scanline = a[1:rb+1]
+                del a[:rb+1]
+                recon = self.undo_filter(filter_type, scanline, recon)
+                yield recon
+        if len(a) != 0:
+            # :file:format We get here with a file format error: when the
+            # available bytes (after decompressing) do not pack into exact
+            # rows.
+            raise FormatError(
+              'Wrong size for decompressed IDAT chunk.')
+        assert len(a) == 0
+
+    def validate_signature(self):
+        """If signature (header) has not been read then read and
+        validate it; otherwise do nothing.
+        """
+
+        if self.signature:
+            return
+        self.signature = self.file.read(8)
+        if self.signature != _signature:
+            raise FormatError("PNG file has invalid signature.")
+
+    def preamble(self):
+        """
+        Extract the image metadata by reading the initial part of the PNG
+        file up to the start of the ``IDAT`` chunk.  All the chunks that
+        precede the ``IDAT`` chunk are read and either processed for
+        metadata or discarded.
+        """
+
+        self.validate_signature()
+
+        while True:
+            if not self.atchunk:
+                self.atchunk = self.chunklentype()
+                if self.atchunk is None:
+                    raise FormatError(
+                      'This PNG file has no IDAT chunks.')
+            if self.atchunk[1] == 'IDAT':
+                return
+            self.process_chunk()
+
+    def chunklentype(self):
+        """Reads just enough of the input to determine the next
+        chunk's length and type, returned as a (*length*, *type*) pair
+        where *type* is a string.  If there are no more chunks, ``None``
+        is returned.
+        """
+
+        x = self.file.read(8)
+        if not x:
+            return None
+        if len(x) != 8:
+            raise FormatError(
+              'End of file whilst reading chunk length and type.')
+        length,type = struct.unpack('!I4s', x)
+        type = bytestostr(type)
+        if length > 2**31-1:
+            raise FormatError('Chunk %s is too large: %d.' % (type,length))
+        return length,type
+
+    def process_chunk(self):
+        """Process the next chunk and its data.  This only processes the
+        following chunk types, all others are ignored: ``IHDR``,
+        ``PLTE``, ``bKGD``, ``tRNS``, ``gAMA``, ``sBIT``.
+        """
+
+        type, data = self.chunk()
+        if type == 'IHDR':
+            # http://www.w3.org/TR/PNG/#11IHDR
+            if len(data) != 13:
+                raise FormatError('IHDR chunk has incorrect length.')
+            (self.width, self.height, self.bitdepth, self.color_type,
+             self.compression, self.filter,
+             self.interlace) = struct.unpack("!2I5B", data)
+
+            # Check that the header specifies only valid combinations.
+            if self.bitdepth not in (1,2,4,8,16):
+                raise Error("invalid bit depth %d" % self.bitdepth)
+            if self.color_type not in (0,2,3,4,6):
+                raise Error("invalid colour type %d" % self.color_type)
+            # Check indexed (palettized) images have 8 or fewer bits
+            # per pixel; check only indexed or greyscale images have
+            # fewer than 8 bits per pixel.
+            if ((self.color_type & 1 and self.bitdepth > 8) or
+                (self.bitdepth < 8 and self.color_type not in (0,3))):
+                raise FormatError("Illegal combination of bit depth (%d)"
+                  " and colour type (%d)."
+                  " See http://www.w3.org/TR/2003/REC-PNG-20031110/#table111 ."
+                  % (self.bitdepth, self.color_type))
+            if self.compression != 0:
+                raise Error("unknown compression method %d" % self.compression)
+            if self.filter != 0:
+                raise FormatError("Unknown filter method %d,"
+                  " see http://www.w3.org/TR/2003/REC-PNG-20031110/#9Filters ."
+                  % self.filter)
+            if self.interlace not in (0,1):
+                raise FormatError("Unknown interlace method %d,"
+                  " see http://www.w3.org/TR/2003/REC-PNG-20031110/#8InterlaceMethods ."
+                  % self.interlace)
+
+            # Derived values
+            # http://www.w3.org/TR/PNG/#6Colour-values
+            colormap =  bool(self.color_type & 1)
+            greyscale = not (self.color_type & 2)
+            alpha = bool(self.color_type & 4)
+            color_planes = (3,1)[greyscale or colormap]
+            planes = color_planes + alpha
+
+            self.colormap = colormap
+            self.greyscale = greyscale
+            self.alpha = alpha
+            self.color_planes = color_planes
+            self.planes = planes
+            self.psize = float(self.bitdepth)/float(8) * planes
+            if int(self.psize) == self.psize:
+                self.psize = int(self.psize)
+            self.row_bytes = int(math.ceil(self.width * self.psize))
+            # Stores PLTE chunk if present, and is used to check
+            # chunk ordering constraints.
+            self.plte = None
+            # Stores tRNS chunk if present, and is used to check chunk
+            # ordering constraints.
+            self.trns = None
+            # Stores sbit chunk if present.
+            self.sbit = None
+        elif type == 'PLTE':
+            # http://www.w3.org/TR/PNG/#11PLTE
+            if self.plte:
+                warnings.warn("Multiple PLTE chunks present.")
+            self.plte = data
+            if len(data) % 3 != 0:
+                raise FormatError(
+                  "PLTE chunk's length should be a multiple of 3.")
+            if len(data) > (2**self.bitdepth)*3:
+                raise FormatError("PLTE chunk is too long.")
+            if len(data) == 0:
+                raise FormatError("Empty PLTE is not allowed.")
+        elif type == 'bKGD':
+            try:
+                if self.colormap:
+                    if not self.plte:
+                        warnings.warn(
+                          "PLTE chunk is required before bKGD chunk.")
+                    self.background = struct.unpack('B', data)
+                else:
+                    self.background = struct.unpack("!%dH" % self.color_planes,
+                      data)
+            except struct.error:
+                raise FormatError("bKGD chunk has incorrect length.")
+        elif type == 'tRNS':
+            # http://www.w3.org/TR/PNG/#11tRNS
+            self.trns = data
+            if self.colormap:
+                if not self.plte:
+                    warnings.warn("PLTE chunk is required before tRNS chunk.")
+                else:
+                    if len(data) > len(self.plte)/3:
+                        # Was warning, but promoted to Error as it
+                        # would otherwise cause pain later on.
+                        raise FormatError("tRNS chunk is too long.")
+            else:
+                if self.alpha:
+                    raise FormatError(
+                      "tRNS chunk is not valid with colour type %d." %
+                      self.color_type)
+                try:
+                    self.transparent = \
+                        struct.unpack("!%dH" % self.color_planes, data)
+                except struct.error:
+                    raise FormatError("tRNS chunk has incorrect length.")
+        elif type == 'gAMA':
+            try:
+                self.gamma = struct.unpack("!L", data)[0] / 100000.0
+            except struct.error:
+                raise FormatError("gAMA chunk has incorrect length.")
+        elif type == 'sBIT':
+            self.sbit = data
+            if (self.colormap and len(data) != 3 or
+                not self.colormap and len(data) != self.planes):
+                raise FormatError("sBIT chunk has incorrect length.")
+
+    def read(self):
+        """
+        Read the PNG file and decode it.  Returns (`width`, `height`,
+        `pixels`, `metadata`).
+
+        May use excessive memory.
+
+        `pixels` are returned in boxed row flat pixel format.
+        """
+
+        def iteridat():
+            """Iterator that yields all the ``IDAT`` chunks as strings."""
+            while True:
+                try:
+                    type, data = self.chunk()
+                except ValueError, e:
+                    raise ChunkError(e.args[0])
+                if type == 'IEND':
+                    # http://www.w3.org/TR/PNG/#11IEND
+                    break
+                if type != 'IDAT':
+                    continue
+                # type == 'IDAT'
+                # http://www.w3.org/TR/PNG/#11IDAT
+                if self.colormap and not self.plte:
+                    warnings.warn("PLTE chunk is required before IDAT chunk")
+                yield data
+
+        def iterdecomp(idat):
+            """Iterator that yields decompressed strings.  `idat` should
+            be an iterator that yields the ``IDAT`` chunk data.
+            """
+
+            # Currently, with no max_length paramter to decompress, this
+            # routine will do one yield per IDAT chunk.  So not very
+            # incremental.
+            d = zlib.decompressobj()
+            # Each IDAT chunk is passed to the decompressor, then any
+            # remaining state is decompressed out.
+            for data in idat:
+                # :todo: add a max_length argument here to limit output
+                # size.
+                yield array('B', d.decompress(data))
+            yield array('B', d.flush())
+
+        self.preamble()
+        raw = iterdecomp(iteridat())
+
+        if self.interlace:
+            raw = array('B', itertools.chain(*raw))
+            arraycode = 'BH'[self.bitdepth>8]
+            # Like :meth:`group` but producing an array.array object for
+            # each row.
+            pixels = itertools.imap(lambda *row: array(arraycode, row),
+                       *[iter(self.deinterlace(raw))]*self.width*self.planes)
+        else:
+            pixels = self.iterboxed(self.iterstraight(raw))
+        meta = dict()
+        for attr in 'greyscale alpha planes bitdepth interlace'.split():
+            meta[attr] = getattr(self, attr)
+        meta['size'] = (self.width, self.height)
+        for attr in 'gamma transparent background'.split():
+            a = getattr(self, attr, None)
+            if a is not None:
+                meta[attr] = a
+        return self.width, self.height, pixels, meta
+
+
+    def read_flat(self):
+        """
+        Read a PNG file and decode it into flat row flat pixel format.
+        Returns (*width*, *height*, *pixels*, *metadata*).
+
+        May use excessive memory.
+
+        `pixels` are returned in flat row flat pixel format.
+
+        See also the :meth:`read` method which returns pixels in the
+        more stream-friendly boxed row flat pixel format.
+        """
+
+        x, y, pixel, meta = self.read()
+        arraycode = 'BH'[meta['bitdepth']>8]
+        pixel = array(arraycode, itertools.chain(*pixel))
+        return x, y, pixel, meta
+
+    def palette(self, alpha='natural'):
+        """Returns a palette that is a sequence of 3-tuples or 4-tuples,
+        synthesizing it from the ``PLTE`` and ``tRNS`` chunks.  These
+        chunks should have already been processed (for example, by
+        calling the :meth:`preamble` method).  All the tuples are the
+        same size: 3-tuples if there is no ``tRNS`` chunk, 4-tuples when
+        there is a ``tRNS`` chunk.  Assumes that the image is colour type
+        3 and therefore a ``PLTE`` chunk is required.
+
+        If the `alpha` argument is ``'force'`` then an alpha channel is
+        always added, forcing the result to be a sequence of 4-tuples.
+        """
+
+        if not self.plte:
+            raise FormatError(
+                "Required PLTE chunk is missing in colour type 3 image.")
+        plte = group(array('B', self.plte), 3)
+        if self.trns or alpha == 'force':
+            trns = array('B', self.trns or '')
+            trns.extend([255]*(len(plte)-len(trns)))
+            plte = map(operator.add, plte, group(trns, 1))
+        return plte
+
+    def asDirect(self):
+        """Returns the image data as a direct representation of an
+        ``x * y * planes`` array.  This method is intended to remove the
+        need for callers to deal with palettes and transparency
+        themselves.  Images with a palette (colour type 3)
+        are converted to RGB or RGBA; images with transparency (a
+        ``tRNS`` chunk) are converted to LA or RGBA as appropriate.
+        When returned in this format the pixel values represent the
+        colour value directly without needing to refer to palettes or
+        transparency information.
+
+        Like the :meth:`read` method this method returns a 4-tuple:
+
+        (*width*, *height*, *pixels*, *meta*)
+
+        This method normally returns pixel values with the bit depth
+        they have in the source image, but when the source PNG has an
+        ``sBIT`` chunk it is inspected and can reduce the bit depth of
+        the result pixels; pixel values will be reduced according to
+        the bit depth specified in the ``sBIT`` chunk (PNG nerds should
+        note a single result bit depth is used for all channels; the
+        maximum of the ones specified in the ``sBIT`` chunk.  An RGB565
+        image will be rescaled to 6-bit RGB666).
+
+        The *meta* dictionary that is returned reflects the `direct`
+        format and not the original source image.  For example, an RGB
+        source image with a ``tRNS`` chunk to represent a transparent
+        colour, will have ``planes=3`` and ``alpha=False`` for the
+        source image, but the *meta* dictionary returned by this method
+        will have ``planes=4`` and ``alpha=True`` because an alpha
+        channel is synthesized and added.
+
+        *pixels* is the pixel data in boxed row flat pixel format (just
+        like the :meth:`read` method).
+
+        All the other aspects of the image data are not changed.
+        """
+
+        self.preamble()
+
+        # Simple case, no conversion necessary.
+        if not self.colormap and not self.trns and not self.sbit:
+            return self.read()
+
+        x,y,pixels,meta = self.read()
+
+        if self.colormap:
+            meta['colormap'] = False
+            meta['alpha'] = bool(self.trns)
+            meta['bitdepth'] = 8
+            meta['planes'] = 3 + bool(self.trns)
+            plte = self.palette()
+            def iterpal(pixels):
+                for row in pixels:
+                    row = map(plte.__getitem__, row)
+                    yield array('B', itertools.chain(*row))
+            pixels = iterpal(pixels)
+        elif self.trns:
+            # It would be nice if there was some reasonable way of doing
+            # this without generating a whole load of intermediate tuples.
+            # But tuples does seem like the easiest way, with no other way
+            # clearly much simpler or much faster.  (Actually, the L to LA
+            # conversion could perhaps go faster (all those 1-tuples!), but
+            # I still wonder whether the code proliferation is worth it)
+            it = self.transparent
+            maxval = 2**meta['bitdepth']-1
+            planes = meta['planes']
+            meta['alpha'] = True
+            meta['planes'] += 1
+            typecode = 'BH'[meta['bitdepth']>8]
+            def itertrns(pixels):
+                for row in pixels:
+                    # For each row we group it into pixels, then form a
+                    # characterisation vector that says whether each pixel
+                    # is opaque or not.  Then we convert True/False to
+                    # 0/maxval (by multiplication), and add it as the extra
+                    # channel.
+                    row = group(row, planes)
+                    opa = map(it.__ne__, row)
+                    opa = map(maxval.__mul__, opa)
+                    opa = zip(opa) # convert to 1-tuples
+                    yield array(typecode,
+                      itertools.chain(*map(operator.add, row, opa)))
+            pixels = itertrns(pixels)
+        targetbitdepth = None
+        if self.sbit:
+            sbit = struct.unpack('%dB' % len(self.sbit), self.sbit)
+            targetbitdepth = max(sbit)
+            if targetbitdepth > meta['bitdepth']:
+                raise Error('sBIT chunk %r exceeds bitdepth %d' %
+                    (sbit,self.bitdepth))
+            if min(sbit) <= 0:
+                raise Error('sBIT chunk %r has a 0-entry' % sbit)
+            if targetbitdepth == meta['bitdepth']:
+                targetbitdepth = None
+        if targetbitdepth:
+            shift = meta['bitdepth'] - targetbitdepth
+            meta['bitdepth'] = targetbitdepth
+            def itershift(pixels):
+                for row in pixels:
+                    yield map(shift.__rrshift__, row)
+            pixels = itershift(pixels)
+        return x,y,pixels,meta
+
+    def asFloat(self, maxval=1.0):
+        """Return image pixels as per :meth:`asDirect` method, but scale
+        all pixel values to be floating point values between 0.0 and
+        *maxval*.
+        """
+
+        x,y,pixels,info = self.asDirect()
+        sourcemaxval = 2**info['bitdepth']-1
+        del info['bitdepth']
+        info['maxval'] = float(maxval)
+        factor = float(maxval)/float(sourcemaxval)
+        def iterfloat():
+            for row in pixels:
+                yield map(factor.__mul__, row)
+        return x,y,iterfloat(),info
+
+    def _as_rescale(self, get, targetbitdepth):
+        """Helper used by :meth:`asRGB8` and :meth:`asRGBA8`."""
+
+        width,height,pixels,meta = get()
+        maxval = 2**meta['bitdepth'] - 1
+        targetmaxval = 2**targetbitdepth - 1
+        factor = float(targetmaxval) / float(maxval)
+        meta['bitdepth'] = targetbitdepth
+        def iterscale():
+            for row in pixels:
+                yield map(lambda x: int(round(x*factor)), row)
+        return width, height, iterscale(), meta
+
+    def asRGB8(self):
+        """Return the image data as an RGB pixels with 8-bits per
+        sample.  This is like the :meth:`asRGB` method except that
+        this method additionally rescales the values so that they
+        are all between 0 and 255 (8-bit).  In the case where the
+        source image has a bit depth < 8 the transformation preserves
+        all the information; where the source image has bit depth
+        > 8, then rescaling to 8-bit values loses precision.  No
+        dithering is performed.  Like :meth:`asRGB`, an alpha channel
+        in the source image will raise an exception.
+
+        This function returns a 4-tuple:
+        (*width*, *height*, *pixels*, *metadata*).
+        *width*, *height*, *metadata* are as per the :meth:`read` method.
+        
+        *pixels* is the pixel data in boxed row flat pixel format.
+        """
+
+        return self._as_rescale(self.asRGB, 8)
+
+    def asRGBA8(self):
+        """Return the image data as RGBA pixels with 8-bits per
+        sample.  This method is similar to :meth:`asRGB8` and
+        :meth:`asRGBA`:  The result pixels have an alpha channel, *and*
+        values are rescaled to the range 0 to 255.  The alpha channel is
+        synthesized if necessary (with a small speed penalty).
+        """
+
+        return self._as_rescale(self.asRGBA, 8)
+
+    def asRGB(self):
+        """Return image as RGB pixels.  RGB colour images are passed
+        through unchanged; greyscales are expanded into RGB
+        triplets (there is a small speed overhead for doing this).
+
+        An alpha channel in the source image will raise an
+        exception.
+
+        The return values are as for the :meth:`read` method
+        except that the *metadata* reflect the returned pixels, not the
+        source image.  In particular, for this method
+        ``metadata['greyscale']`` will be ``False``.
+        """
+
+        width,height,pixels,meta = self.asDirect()
+        if meta['alpha']:
+            raise Error("will not convert image with alpha channel to RGB")
+        if not meta['greyscale']:
+            return width,height,pixels,meta
+        meta['greyscale'] = False
+        typecode = 'BH'[meta['bitdepth'] > 8]
+        def iterrgb():
+            for row in pixels:
+                a = array(typecode, [0]) * 3 * width
+                for i in range(3):
+                    a[i::3] = row
+                yield a
+        return width,height,iterrgb(),meta
+
+    def asRGBA(self):
+        """Return image as RGBA pixels.  Greyscales are expanded into
+        RGB triplets; an alpha channel is synthesized if necessary.
+        The return values are as for the :meth:`read` method
+        except that the *metadata* reflect the returned pixels, not the
+        source image.  In particular, for this method
+        ``metadata['greyscale']`` will be ``False``, and
+        ``metadata['alpha']`` will be ``True``.
+        """
+
+        width,height,pixels,meta = self.asDirect()
+        if meta['alpha'] and not meta['greyscale']:
+            return width,height,pixels,meta
+        typecode = 'BH'[meta['bitdepth'] > 8]
+        maxval = 2**meta['bitdepth'] - 1
+        def newarray():
+            return array(typecode, [0]) * 4 * width
+        if meta['alpha'] and meta['greyscale']:
+            # LA to RGBA
+            def convert():
+                for row in pixels:
+                    # Create a fresh target row, then copy L channel
+                    # into first three target channels, and A channel
+                    # into fourth channel.
+                    a = newarray()
+                    for i in range(3):
+                        a[i::4] = row[0::2]
+                    a[3::4] = row[1::2]
+                    yield a
+        elif meta['greyscale']:
+            # L to RGBA
+            def convert():
+                for row in pixels:
+                    a = newarray()
+                    for i in range(3):
+                        a[i::4] = row
+                    a[3::4] = array(typecode, [maxval]) * width
+                    yield a
+        else:
+            assert not meta['alpha'] and not meta['greyscale']
+            # RGB to RGBA
+            def convert():
+                for row in pixels:
+                    a = newarray()
+                    for i in range(3):
+                        a[i::4] = row[i::3]
+                    a[3::4] = array(typecode, [maxval]) * width
+                    yield a
+        meta['alpha'] = True
+        meta['greyscale'] = False
+        return width,height,convert(),meta
+
+
+# === Legacy Version Support ===
+
+# :pyver:old:  PyPNG works on Python versions 2.3 and 2.2, but not
+# without some awkward problems.  Really PyPNG works on Python 2.4 (and
+# above); it works on Pythons 2.3 and 2.2 by virtue of fixing up
+# problems here.  It's a bit ugly (which is why it's hidden down here).
+#
+# Generally the strategy is one of pretending that we're running on
+# Python 2.4 (or above), and patching up the library support on earlier
+# versions so that it looks enough like Python 2.4.  When it comes to
+# Python 2.2 there is one thing we cannot patch: extended slices
+# http://www.python.org/doc/2.3/whatsnew/section-slices.html.
+# Instead we simply declare that features that are implemented using
+# extended slices will not work on Python 2.2.
+#
+# In order to work on Python 2.3 we fix up a recurring annoyance involving
+# the array type.  In Python 2.3 an array cannot be initialised with an
+# array, and it cannot be extended with a list (or other sequence).
+# Both of those are repeated issues in the code.  Whilst I would not
+# normally tolerate this sort of behaviour, here we "shim" a replacement
+# for array into place (and hope no-ones notices).  You never read this.
+#
+# In an amusing case of warty hacks on top of warty hacks... the array
+# shimming we try and do only works on Python 2.3 and above (you can't
+# subclass array.array in Python 2.2).  So to get it working on Python
+# 2.2 we go for something much simpler and (probably) way slower.
+try:
+    array('B').extend([])
+    array('B', array('B'))
+except:
+    # Expect to get here on Python 2.3
+    try:
+        class _array_shim(array):
+            true_array = array
+            def __new__(cls, typecode, init=None):
+                super_new = super(_array_shim, cls).__new__
+                it = super_new(cls, typecode)
+                if init is None:
+                    return it
+                it.extend(init)
+                return it
+            def extend(self, extension):
+                super_extend = super(_array_shim, self).extend
+                if isinstance(extension, self.true_array):
+                    return super_extend(extension)
+                if not isinstance(extension, (list, str)):
+                    # Convert to list.  Allows iterators to work.
+                    extension = list(extension)
+                return super_extend(self.true_array(self.typecode, extension))
+        array = _array_shim
+    except:
+        # Expect to get here on Python 2.2
+        def array(typecode, init=()):
+            if type(init) == str:
+                return map(ord, init)
+            return list(init)
+
+# Further hacks to get it limping along on Python 2.2
+try:
+    enumerate
+except:
+    def enumerate(seq):
+        i=0
+        for x in seq:
+            yield i,x
+            i += 1
+
+try:
+    reversed
+except:
+    def reversed(l):
+        l = list(l)
+        l.reverse()
+        for x in l:
+            yield x
+
+try:
+    itertools
+except:
+    class _dummy_itertools:
+        pass
+    itertools = _dummy_itertools()
+    def _itertools_imap(f, seq):
+        for x in seq:
+            yield f(x)
+    itertools.imap = _itertools_imap
+    def _itertools_chain(*iterables):
+        for it in iterables:
+            for element in it:
+                yield element
+    itertools.chain = _itertools_chain
+
+
+
+# === Internal Test Support ===
+
+# This section comprises the tests that are internally validated (as
+# opposed to tests which produce output files that are externally
+# validated).  Primarily they are unittests.
+
+# Note that it is difficult to internally validate the results of
+# writing a PNG file.  The only thing we can do is read it back in
+# again, which merely checks consistency, not that the PNG file we
+# produce is valid.
+
+# Run the tests from the command line:
+# python -c 'import png;png.test()'
+
+# (For an in-memory binary file IO object) We use BytesIO where
+# available, otherwise we use StringIO, but name it BytesIO.
+try:
+    from io import BytesIO
+except:
+    from StringIO import StringIO as BytesIO
+import tempfile
+# http://www.python.org/doc/2.4.4/lib/module-unittest.html
+import unittest
+
+
+def test():
+    unittest.main(__name__)
+
+def topngbytes(name, rows, x, y, **k):
+    """Convenience function for creating a PNG file "in memory" as a
+    string.  Creates a :class:`Writer` instance using the keyword arguments,
+    then passes `rows` to its :meth:`Writer.write` method.  The resulting
+    PNG file is returned as a string.  `name` is used to identify the file for
+    debugging.
+    """
+
+    import os
+
+    print name
+    f = BytesIO()
+    w = Writer(x, y, **k)
+    w.write(f, rows)
+    if os.environ.get('PYPNG_TEST_TMP'):
+        w = open(name, 'wb')
+        w.write(f.getvalue())
+        w.close()
+    return f.getvalue()
+
+def testWithIO(inp, out, f):
+    """Calls the function `f` with ``sys.stdin`` changed to `inp`
+    and ``sys.stdout`` changed to `out`.  They are restored when `f`
+    returns.  This function returns whatever `f` returns.
+    """
+
+    import os
+
+    try:
+        oldin,sys.stdin = sys.stdin,inp
+        oldout,sys.stdout = sys.stdout,out
+        x = f()
+    finally:
+        sys.stdin = oldin
+        sys.stdout = oldout
+    if os.environ.get('PYPNG_TEST_TMP') and hasattr(out,'getvalue'):
+        name = mycallersname()
+        if name:
+            w = open(name+'.png', 'wb')
+            w.write(out.getvalue())
+            w.close()
+    return x
+
+def mycallersname():
+    """Returns the name of the caller of the caller of this function
+    (hence the name of the caller of the function in which
+    "mycallersname()" textually appears).  Returns None if this cannot
+    be determined."""
+
+    # http://docs.python.org/library/inspect.html#the-interpreter-stack
+    import inspect
+
+    frame = inspect.currentframe()
+    if not frame:
+        return None
+    frame_,filename_,lineno_,funname,linelist_,listi_ = (
+      inspect.getouterframes(frame)[2])
+    return funname
+
+def seqtobytes(s):
+    """Convert a sequence of integers to a *bytes* instance.  Good for
+    plastering over Python 2 / Python 3 cracks.
+    """
+
+    return strtobytes(''.join(chr(x) for x in s))
+
+class Test(unittest.TestCase):
+    # This member is used by the superclass.  If we don't define a new
+    # class here then when we use self.assertRaises() and the PyPNG code
+    # raises an assertion then we get no proper traceback.  I can't work
+    # out why, but defining a new class here means we get a proper
+    # traceback.
+    class failureException(Exception):
+        pass
+
+    def helperLN(self, n):
+        mask = (1 << n) - 1
+        # Use small chunk_limit so that multiple chunk writing is
+        # tested.  Making it a test for Issue 20.
+        w = Writer(15, 17, greyscale=True, bitdepth=n, chunk_limit=99)
+        f = BytesIO()
+        w.write_array(f, array('B', map(mask.__and__, range(1, 256))))
+        r = Reader(bytes=f.getvalue())
+        x,y,pixels,meta = r.read()
+        self.assertEqual(x, 15)
+        self.assertEqual(y, 17)
+        self.assertEqual(list(itertools.chain(*pixels)),
+                         map(mask.__and__, range(1,256)))
+    def testL8(self):
+        return self.helperLN(8)
+    def testL4(self):
+        return self.helperLN(4)
+    def testL2(self):
+        "Also tests asRGB8."
+        w = Writer(1, 4, greyscale=True, bitdepth=2)
+        f = BytesIO()
+        w.write_array(f, array('B', range(4)))
+        r = Reader(bytes=f.getvalue())
+        x,y,pixels,meta = r.asRGB8()
+        self.assertEqual(x, 1)
+        self.assertEqual(y, 4)
+        for i,row in enumerate(pixels):
+            self.assertEqual(len(row), 3)
+            self.assertEqual(list(row), [0x55*i]*3)
+    def testP2(self):
+        "2-bit palette."
+        a = (255,255,255)
+        b = (200,120,120)
+        c = (50,99,50)
+        w = Writer(1, 4, bitdepth=2, palette=[a,b,c])
+        f = BytesIO()
+        w.write_array(f, array('B', (0,1,1,2)))
+        r = Reader(bytes=f.getvalue())
+        x,y,pixels,meta = r.asRGB8()
+        self.assertEqual(x, 1)
+        self.assertEqual(y, 4)
+        self.assertEqual(list(pixels), map(list, [a, b, b, c]))
+    def testPtrns(self):
+        "Test colour type 3 and tRNS chunk (and 4-bit palette)."
+        a = (50,99,50,50)
+        b = (200,120,120,80)
+        c = (255,255,255)
+        d = (200,120,120)
+        e = (50,99,50)
+        w = Writer(3, 3, bitdepth=4, palette=[a,b,c,d,e])
+        f = BytesIO()
+        w.write_array(f, array('B', (4, 3, 2, 3, 2, 0, 2, 0, 1)))
+        r = Reader(bytes=f.getvalue())
+        x,y,pixels,meta = r.asRGBA8()
+        self.assertEqual(x, 3)
+        self.assertEqual(y, 3)
+        c = c+(255,)
+        d = d+(255,)
+        e = e+(255,)
+        boxed = [(e,d,c),(d,c,a),(c,a,b)]
+        flat = map(lambda row: itertools.chain(*row), boxed)
+        self.assertEqual(map(list, pixels), map(list, flat))
+    def testRGBtoRGBA(self):
+        "asRGBA8() on colour type 2 source."""
+        # Test for Issue 26
+        r = Reader(bytes=_pngsuite['basn2c08'])
+        x,y,pixels,meta = r.asRGBA8()
+        # Test the pixels at row 9 columns 0 and 1.
+        row9 = list(pixels)[9]
+        self.assertEqual(row9[0:8],
+                         [0xff, 0xdf, 0xff, 0xff, 0xff, 0xde, 0xff, 0xff])
+    def testLtoRGBA(self):
+        "asRGBA() on grey source."""
+        # Test for Issue 60
+        r = Reader(bytes=_pngsuite['basi0g08'])
+        x,y,pixels,meta = r.asRGBA()
+        row9 = list(list(pixels)[9])
+        self.assertEqual(row9[0:8],
+          [222, 222, 222, 255, 221, 221, 221, 255])
+    def testCtrns(self):
+        "Test colour type 2 and tRNS chunk."
+        # Test for Issue 25
+        r = Reader(bytes=_pngsuite['tbrn2c08'])
+        x,y,pixels,meta = r.asRGBA8()
+        # I just happen to know that the first pixel is transparent.
+        # In particular it should be #7f7f7f00
+        row0 = list(pixels)[0]
+        self.assertEqual(tuple(row0[0:4]), (0x7f, 0x7f, 0x7f, 0x00))
+    def testAdam7read(self):
+        """Adam7 interlace reading.
+        Specifically, test that for images in the PngSuite that
+        have both an interlaced and straightlaced pair that both
+        images from the pair produce the same array of pixels."""
+        for candidate in _pngsuite:
+            if not candidate.startswith('basn'):
+                continue
+            candi = candidate.replace('n', 'i')
+            if candi not in _pngsuite:
+                continue
+            print 'adam7 read', candidate
+            straight = Reader(bytes=_pngsuite[candidate])
+            adam7 = Reader(bytes=_pngsuite[candi])
+            # Just compare the pixels.  Ignore x,y (because they're
+            # likely to be correct?); metadata is ignored because the
+            # "interlace" member differs.  Lame.
+            straight = straight.read()[2]
+            adam7 = adam7.read()[2]
+            self.assertEqual(map(list, straight), map(list, adam7))
+    def testAdam7write(self):
+        """Adam7 interlace writing.
+        For each test image in the PngSuite, write an interlaced
+        and a straightlaced version.  Decode both, and compare results.
+        """
+        # Not such a great test, because the only way we can check what
+        # we have written is to read it back again.
+
+        for name,bytes in _pngsuite.items():
+            # Only certain colour types supported for this test.
+            if name[3:5] not in ['n0', 'n2', 'n4', 'n6']:
+                continue
+            it = Reader(bytes=bytes)
+            x,y,pixels,meta = it.read()
+            pngi = topngbytes('adam7wn'+name+'.png', pixels,
+              x=x, y=y, bitdepth=it.bitdepth,
+              greyscale=it.greyscale, alpha=it.alpha,
+              transparent=it.transparent,
+              interlace=False)
+            x,y,ps,meta = Reader(bytes=pngi).read()
+            it = Reader(bytes=bytes)
+            x,y,pixels,meta = it.read()
+            pngs = topngbytes('adam7wi'+name+'.png', pixels,
+              x=x, y=y, bitdepth=it.bitdepth,
+              greyscale=it.greyscale, alpha=it.alpha,
+              transparent=it.transparent,
+              interlace=True)
+            x,y,pi,meta = Reader(bytes=pngs).read()
+            self.assertEqual(map(list, ps), map(list, pi))
+    def testPGMin(self):
+        """Test that the command line tool can read PGM files."""
+        def do():
+            return _main(['testPGMin'])
+        s = BytesIO()
+        s.write(strtobytes('P5 2 2 3\n'))
+        s.write(strtobytes('\x00\x01\x02\x03'))
+        s.flush()
+        s.seek(0)
+        o = BytesIO()
+        testWithIO(s, o, do)
+        r = Reader(bytes=o.getvalue())
+        x,y,pixels,meta = r.read()
+        self.assertTrue(r.greyscale)
+        self.assertEqual(r.bitdepth, 2)
+    def testPAMin(self):
+        """Test that the command line tool can read PAM file."""
+        def do():
+            return _main(['testPAMin'])
+        s = BytesIO()
+        s.write(strtobytes('P7\nWIDTH 3\nHEIGHT 1\nDEPTH 4\nMAXVAL 255\n'
+                'TUPLTYPE RGB_ALPHA\nENDHDR\n'))
+        # The pixels in flat row flat pixel format
+        flat =  [255,0,0,255, 0,255,0,120, 0,0,255,30]
+        asbytes = seqtobytes(flat)
+        s.write(asbytes)
+        s.flush()
+        s.seek(0)
+        o = BytesIO()
+        testWithIO(s, o, do)
+        r = Reader(bytes=o.getvalue())
+        x,y,pixels,meta = r.read()
+        self.assertTrue(r.alpha)
+        self.assertTrue(not r.greyscale)
+        self.assertEqual(list(itertools.chain(*pixels)), flat)
+    def testLA4(self):
+        """Create an LA image with bitdepth 4."""
+        bytes = topngbytes('la4.png', [[5, 12]], 1, 1,
+          greyscale=True, alpha=True, bitdepth=4)
+        sbit = Reader(bytes=bytes).chunk('sBIT')[1]
+        self.assertEqual(sbit, strtobytes('\x04\x04'))
+    def testPNMsbit(self):
+        """Test that PNM files can generates sBIT chunk."""
+        def do():
+            return _main(['testPNMsbit'])
+        s = BytesIO()
+        s.write(strtobytes('P6 8 1 1\n'))
+        for pixel in range(8):
+            s.write(struct.pack('<I', (0x4081*pixel)&0x10101)[:3])
+        s.flush()
+        s.seek(0)
+        o = BytesIO()
+        testWithIO(s, o, do)
+        r = Reader(bytes=o.getvalue())
+        sbit = r.chunk('sBIT')[1]
+        self.assertEqual(sbit, strtobytes('\x01\x01\x01'))
+    def testLtrns0(self):
+        """Create greyscale image with tRNS chunk."""
+        return self.helperLtrns(0)
+    def testLtrns1(self):
+        """Using 1-tuple for transparent arg."""
+        return self.helperLtrns((0,))
+    def helperLtrns(self, transparent):
+        """Helper used by :meth:`testLtrns*`."""
+        pixels = zip([0x00, 0x38, 0x4c, 0x54, 0x5c, 0x40, 0x38, 0x00])
+        o = BytesIO()
+        w = Writer(8, 8, greyscale=True, bitdepth=1, transparent=transparent)
+        w.write_packed(o, pixels)
+        r = Reader(bytes=o.getvalue())
+        x,y,pixels,meta = r.asDirect()
+        self.assertTrue(meta['alpha'])
+        self.assertTrue(meta['greyscale'])
+        self.assertEqual(meta['bitdepth'], 1)
+    def testWinfo(self):
+        """Test the dictionary returned by a `read` method can be used
+        as args for :meth:`Writer`.
+        """
+        r = Reader(bytes=_pngsuite['basn2c16'])
+        info = r.read()[3]
+        w = Writer(**info)
+    def testPackedIter(self):
+        """Test iterator for row when using write_packed.
+
+        Indicative for Issue 47.
+        """
+        w = Writer(16, 2, greyscale=True, alpha=False, bitdepth=1)
+        o = BytesIO()
+        w.write_packed(o, [itertools.chain([0x0a], [0xaa]),
+                           itertools.chain([0x0f], [0xff])])
+        r = Reader(bytes=o.getvalue())
+        x,y,pixels,info = r.asDirect()
+        pixels = list(pixels)
+        self.assertEqual(len(pixels), 2)
+        self.assertEqual(len(pixels[0]), 16)
+    def testInterlacedArray(self):
+        """Test that reading an interlaced PNG yields each row as an
+        array."""
+        r = Reader(bytes=_pngsuite['basi0g08'])
+        list(r.read()[2])[0].tostring
+    def testTrnsArray(self):
+        """Test that reading a type 2 PNG with tRNS chunk yields each
+        row as an array (using asDirect)."""
+        r = Reader(bytes=_pngsuite['tbrn2c08'])
+        list(r.asDirect()[2])[0].tostring
+
+    # Invalid file format tests.  These construct various badly
+    # formatted PNG files, then feed them into a Reader.  When
+    # everything is working properly, we should get FormatError
+    # exceptions raised.
+    def testEmpty(self):
+        """Test empty file."""
+
+        r = Reader(bytes='')
+        self.assertRaises(FormatError, r.asDirect)
+    def testSigOnly(self):
+        """Test file containing just signature bytes."""
+
+        r = Reader(bytes=_signature)
+        self.assertRaises(FormatError, r.asDirect)
+    def testExtraPixels(self):
+        """Test file that contains too many pixels."""
+
+        def eachchunk(chunk):
+            if chunk[0] != 'IDAT':
+                return chunk
+            data = zlib.decompress(chunk[1])
+            data += strtobytes('\x00garbage')
+            data = zlib.compress(data)
+            chunk = (chunk[0], data)
+            return chunk
+        self.assertRaises(FormatError, self.helperFormat, eachchunk)
+    def testNotEnoughPixels(self):
+        def eachchunk(chunk):
+            if chunk[0] != 'IDAT':
+                return chunk
+            # Remove last byte.
+            data = zlib.decompress(chunk[1])
+            data = data[:-1]
+            data = zlib.compress(data)
+            return (chunk[0], data)
+        self.assertRaises(FormatError, self.helperFormat, eachchunk)
+    def helperFormat(self, f):
+        r = Reader(bytes=_pngsuite['basn0g01'])
+        o = BytesIO()
+        def newchunks():
+            for chunk in r.chunks():
+                yield f(chunk)
+        write_chunks(o, newchunks())
+        r = Reader(bytes=o.getvalue())
+        return list(r.asDirect()[2])
+    def testBadFilter(self):
+        def eachchunk(chunk):
+            if chunk[0] != 'IDAT':
+                return chunk
+            data = zlib.decompress(chunk[1])
+            # Corrupt the first filter byte
+            data = strtobytes('\x99') + data[1:]
+            data = zlib.compress(data)
+            return (chunk[0], data)
+        self.assertRaises(FormatError, self.helperFormat, eachchunk)
+    def testFlat(self):
+        """Test read_flat."""
+        import hashlib
+
+        r = Reader(bytes=_pngsuite['basn0g02'])
+        x,y,pixel,meta = r.read_flat()
+        d = hashlib.md5(seqtobytes(pixel)).digest()
+        self.assertEqual(_enhex(d), '255cd971ab8cd9e7275ff906e5041aa0')
+    def testfromarray(self):
+        img = from_array([[0, 0x33, 0x66], [0xff, 0xcc, 0x99]], 'L')
+        img.save('testfromarray.png')
+    def testfromarrayL16(self):
+        img = from_array(group(range(2**16), 256), 'L;16')
+        img.save('testL16.png')
+    def testfromarrayRGB(self):
+        img = from_array([[0,0,0, 0,0,1, 0,1,0, 0,1,1],
+                          [1,0,0, 1,0,1, 1,1,0, 1,1,1]], 'RGB;1')
+        o = BytesIO()
+        img.save(o)
+    def testfromarrayIter(self):
+        import itertools
+
+        i = itertools.islice(itertools.count(10), 20)
+        i = itertools.imap(lambda x: [x, x, x], i)
+        img = from_array(i, 'RGB;5', dict(height=20))
+        f = open('testiter.png', 'wb')
+        img.save(f)
+        f.close()
+
+    # numpy dependent tests.  These are skipped (with a message to
+    # sys.stderr) if numpy cannot be imported.
+    def testNumpyuint16(self):
+        """numpy uint16."""
+
+        try:
+            import numpy
+        except ImportError:
+            print >>sys.stderr, "skipping numpy test"
+            return
+
+        rows = [map(numpy.uint16, range(0,0x10000,0x5555))]
+        b = topngbytes('numpyuint16.png', rows, 4, 1,
+            greyscale=True, alpha=False, bitdepth=16)
+    def testNumpyuint8(self):
+        """numpy uint8."""
+
+        try:
+            import numpy
+        except ImportError:
+            print >>sys.stderr, "skipping numpy test"
+            return
+
+        rows = [map(numpy.uint8, range(0,0x100,0x55))]
+        b = topngbytes('numpyuint8.png', rows, 4, 1,
+            greyscale=True, alpha=False, bitdepth=8)
+    def testNumpybool(self):
+        """numpy bool."""
+
+        try:
+            import numpy
+        except ImportError:
+            print >>sys.stderr, "skipping numpy test"
+            return
+
+        rows = [map(numpy.bool, [0,1])]
+        b = topngbytes('numpybool.png', rows, 2, 1,
+            greyscale=True, alpha=False, bitdepth=1)
+    def testNumpyarray(self):
+        """numpy array."""
+        try:
+            import numpy
+        except ImportError:
+            print >>sys.stderr, "skipping numpy test"
+            return
+
+        pixels = numpy.array([[0,0x5555],[0x5555,0xaaaa]], numpy.uint16)
+        img = from_array(pixels, 'L')
+        img.save('testnumpyL16.png')
+
+# === Command Line Support ===
+
+def _dehex(s):
+    """Liberally convert from hex string to binary string."""
+    import re
+    import binascii
+
+    # Remove all non-hexadecimal digits
+    s = re.sub(r'[^a-fA-F\d]', '', s)
+    # binscii.unhexlify works in Python 2 and Python 3 (unlike
+    # thing.decode('hex')).
+    return binascii.unhexlify(strtobytes(s))
+def _enhex(s):
+    """Convert from binary string (bytes) to hex string (str)."""
+
+    import binascii
+
+    return bytestostr(binascii.hexlify(s))
+
+# Copies of PngSuite test files taken
+# from http://www.schaik.com/pngsuite/pngsuite_bas_png.html
+# on 2009-02-19 by drj and converted to hex.
+# Some of these are not actually in PngSuite (but maybe they should
+# be?), they use the same naming scheme, but start with a capital
+# letter.
+_pngsuite = {
+  'basi0g01': _dehex("""
+89504e470d0a1a0a0000000d49484452000000200000002001000000012c0677
+cf0000000467414d41000186a031e8965f0000009049444154789c2d8d310ec2
+300c45dfc682c415187a00a42e197ab81e83b127e00c5639001363a580d8582c
+65c910357c4b78b0bfbfdf4f70168c19e7acb970a3f2d1ded9695ce5bf5963df
+d92aaf4c9fd927ea449e6487df5b9c36e799b91bdf082b4d4bd4014fe4014b01
+ab7a17aee694d28d328a2d63837a70451e1648702d9a9ff4a11d2f7a51aa21e5
+a18c7ffd0094e3511d661822f20000000049454e44ae426082
+"""),
+  'basi0g02': _dehex("""
+89504e470d0a1a0a0000000d49484452000000200000002002000000016ba60d
+1f0000000467414d41000186a031e8965f0000005149444154789c635062e860
+00e17286bb609c93c370ec189494960631366e4467b3ae675dcf10f521ea0303
+90c1ca006444e11643482064114a4852c710baea3f18c31918020c30410403a6
+0ac1a09239009c52804d85b6d97d0000000049454e44ae426082
+"""),
+  'basi0g04': _dehex("""
+89504e470d0a1a0a0000000d4948445200000020000000200400000001e4e6f8
+bf0000000467414d41000186a031e8965f000000ae49444154789c658e5111c2
+301044171c141c141c041c843a287510ea20d441c041c141c141c04191102454
+03994998cecd7edcecedbb9bdbc3b2c2b6457545fbc4bac1be437347f7c66a77
+3c23d60db15e88f5c5627338a5416c2e691a9b475a89cd27eda12895ae8dfdab
+43d61e590764f5c83a226b40d669bec307f93247701687723abf31ff83a2284b
+a5b4ae6b63ac6520ad730ca4ed7b06d20e030369bd6720ed383290360406d24e
+13811f2781eba9d34d07160000000049454e44ae426082
+"""),
+  'basi0g08': _dehex("""
+89504e470d0a1a0a0000000d4948445200000020000000200800000001211615
+be0000000467414d41000186a031e8965f000000b549444154789cb5905d0ac2
+3010849dbac81c42c47bf843cf253e8878b0aa17110f214bdca6be240f5d21a5
+94ced3e49bcd322c1624115515154998aa424822a82a5624a1aa8a8b24c58f99
+999908130989a04a00d76c2c09e76cf21adcb209393a6553577da17140a2c59e
+70ecbfa388dff1f03b82fb82bd07f05f7cb13f80bb07ad2fd60c011c3c588eef
+f1f4e03bbec7ce832dca927aea005e431b625796345307b019c845e6bfc3bb98
+769d84f9efb02ea6c00f9bb9ff45e81f9f280000000049454e44ae426082
+"""),
+  'basi0g16': _dehex("""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+"""),
+  'basi2c08': _dehex("""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+"""),
+  'basi2c16': _dehex("""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+"""),
+  'basi3p08': _dehex("""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+"""),
+  'basi6a08': _dehex("""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+"""),
+  'basn0g01': _dehex("""
+89504e470d0a1a0a0000000d49484452000000200000002001000000005b0147
+590000000467414d41000186a031e8965f0000005b49444154789c2dccb10903
+300c05d1ebd204b24a200b7a346f90153c82c18d0a61450751f1e08a2faaead2
+a4846ccea9255306e753345712e211b221bf4b263d1b427325255e8bdab29e6f
+6aca30692e9d29616ee96f3065f0bf1f1087492fd02f14c90000000049454e44
+ae426082
+"""),
+  'basn0g02': _dehex("""
+89504e470d0a1a0a0000000d49484452000000200000002002000000001ca13d
+890000000467414d41000186a031e8965f0000001f49444154789c6360085df5
+1f8cf1308850c20053868f0133091f6390b90700bd497f818b0989a900000000
+49454e44ae426082
+"""),
+  # A version of basn0g04 dithered down to 3 bits.
+  'Basn0g03': _dehex("""
+89504e470d0a1a0a0000000d494844520000002000000020040000000093e1c8
+2900000001734249540371d88211000000fd49444154789c6d90d18906210c84
+c356f22356b2889588604301b112112b11d94a96bb495cf7fe87f32d996f2689
+44741cc658e39c0b118f883e1f63cc89dafbc04c0f619d7d898396c54b875517
+83f3a2e7ac09a2074430e7f497f00f1138a5444f82839c5206b1f51053cca968
+63258821e7f2b5438aac16fbecc052b646e709de45cf18996b29648508728612
+952ca606a73566d44612b876845e9a347084ea4868d2907ff06be4436c4b41a3
+a3e1774285614c5affb40dbd931a526619d9fa18e4c2be420858de1df0e69893
+a0e3e5523461be448561001042b7d4a15309ce2c57aef2ba89d1c13794a109d7
+b5880aa27744fc5c4aecb5e7bcef5fe528ec6293a930690000000049454e44ae
+426082
+"""),
+  'basn0g04': _dehex("""
+89504e470d0a1a0a0000000d494844520000002000000020040000000093e1c8
+290000000467414d41000186a031e8965f0000004849444154789c6360601014
+545232367671090d4d4b2b2f6720430095dbd1418e002a77e64c720450b9ab56
+912380caddbd9b1c0154ee9933e408a072efde25470095fbee1d1902001f14ee
+01eaff41fa0000000049454e44ae426082
+"""),
+  'basn0g08': _dehex("""
+89504e470d0a1a0a0000000d4948445200000020000000200800000000561125
+280000000467414d41000186a031e8965f0000004149444154789c6364602400
+1408c8b30c05058c0f0829f8f71f3f6079301c1430ca11906764a2795c0c0605
+8c8ff0cafeffcff887e67131181430cae0956564040050e5fe7135e2d8590000
+000049454e44ae426082
+"""),
+  'basn0g16': _dehex("""
+89504e470d0a1a0a0000000d49484452000000200000002010000000000681f9
+6b0000000467414d41000186a031e8965f0000005e49444154789cd5d2310ac0
+300c4351395bef7fc6dca093c0287b32d52a04a3d98f3f3880a7b857131363a0
+3a82601d089900dd82f640ca04e816dc06422640b7a03d903201ba05b7819009
+d02d680fa44c603f6f07ec4ff41938cf7f0016d84bd85fae2b9fd70000000049
+454e44ae426082
+"""),
+  'basn2c08': _dehex("""
+89504e470d0a1a0a0000000d4948445200000020000000200802000000fc18ed
+a30000000467414d41000186a031e8965f0000004849444154789cedd5c10900
+300c024085ec91fdb772133b442bf4a1f8cee12bb40d043b800a14f81ca0ede4
+7d4c784081020f4a871fc284071428f0a0743823a94081bb7077a3c00182b1f9
+5e0f40cf4b0000000049454e44ae426082
+"""),
+  'basn2c16': _dehex("""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+"""),
+  'basn6a08': _dehex("""
+89504e470d0a1a0a0000000d4948445200000020000000200806000000737a7a
+f40000000467414d41000186a031e8965f0000006f49444154789cedd6310a80
+300c46e12764684fa1f73f55048f21c4ddc545781d52e85028fc1f4d28d98a01
+305e7b7e9cffba33831d75054703ca06a8f90d58a0074e351e227d805c8254e3
+1bb0420f5cdc2e0079208892ffe2a00136a07b4007943c1004d900195036407f
+011bf00052201a9c160fb84c0000000049454e44ae426082
+"""),
+  'cs3n3p08': _dehex("""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+"""),
+  's09n3p02': _dehex("""
+89504e470d0a1a0a0000000d49484452000000090000000902030000009dffee
+830000000467414d41000186a031e8965f000000037342495404040477f8b5a3
+0000000c504c544500ff000077ffff00ffff7700ff5600640000001f49444154
+789c63600002fbff0c0c56ab19182ca381581a4283f82071200000696505c36a
+437f230000000049454e44ae426082
+"""),
+  'tbgn3p08': _dehex("""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+"""),
+  'Tp2n3p08': _dehex("""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+"""),
+  'tbbn1g04': _dehex("""
+89504e470d0a1a0a0000000d494844520000002000000020040000000093e1c8
+290000000467414d41000186a031e8965f0000000274524e530007e8f7589b00
+000002624b47440000aa8d23320000013e49444154789c55d1cd4b024118c7f1
+efbe6419045b6a48a72d352808b435284f9187ae9b098627a1573a19945beba5
+e8129e8222af11d81e3a4545742de8ef6af6d5762e0fbf0fc33c33f36085cb76
+bc4204778771b867260683ee57e13f0c922df5c719c2b3b6c6c25b2382cea4b9
+9f7d4f244370746ac71f4ca88e0f173a6496749af47de8e44ba8f3bf9bdfa98a
+0faf857a7dd95c7dc8d7c67c782c99727997f41eb2e3c1e554152465bb00fe8e
+b692d190b718d159f4c0a45c4435915a243c58a7a4312a7a57913f05747594c6
+46169866c57101e4d4ce4d511423119c419183a3530cc63db88559ae28e7342a
+1e9c8122b71139b8872d6e913153224bc1f35b60e4445bd4004e20ed6682c759
+1d9873b3da0fbf50137dc5c9bde84fdb2ec8bde1189e0448b63584735993c209
+7a601bd2710caceba6158797285b7f2084a2f82c57c01a0000000049454e44ae
+426082
+"""),
+  'tbrn2c08': _dehex("""
+89504e470d0a1a0a0000000d4948445200000020000000200802000000fc18ed
+a30000000467414d41000186a031e8965f0000000674524e53007f007f007f8a
+33334f00000006624b474400ff0000000033277cf3000004d649444154789cad
+965f68537714c73fd912d640235e692f34d0406fa0c1663481045ab060065514
+56660a295831607df0a1488715167060840a1614e6431e9cb34fd2c00a762c85
+f6a10f816650c13b0cf40612e1822ddc4863bd628a8924d23d6464f9d3665dd9
+f7e977ce3dbff3cd3939bfdfef6bb87dfb364782dbed065ebe7cd93acc78b4ec
+a228debd7bb7bfbfbfbbbbfb7f261045311a8d261209405194274f9ea4d3e916
+f15f1c3eb5dd6e4fa5fecce526239184a2b0b8486f6f617171b1f5ae4311381c
+8e57af5e5dbd7a351088150a78bd389d44222c2f93cdfe66b7db8f4ee07038b6
+b6b6bebf766d7e7e7e60a06432313b4ba984c3c1c4049a46b95c5a58583822c1
+dbb76f27272733d1b9df853c3030c0f232562b9108cf9eb1b888d7cbf030abab
+31abd5fa1f08dc6ef7e7cf9f1f3f7e1c8944745d4f1400c62c001313acad21cb
+b8dd2c2c603271eb1640341aad4c6d331aa7e8c48913a150a861307ecc11e964
+74899919bc5e14e56fffc404f1388502f178dceff7ef4bf0a5cfe7abb533998c
+e5f9ea2f1dd88c180d64cb94412df3dd57e83a6b3b3c7a84c98420100c72fd3a
+636348bae726379fe69e8e8d8dbd79f3a6558b0607079796965256479b918085
+7b02db12712b6181950233023f3f647494ee6e2e5ea45864cce5b8a7fe3acffc
+3aebb22c2bd5d20e22d0757d7b7bbbbdbd3d94a313bed1b0aa3cd069838b163a
+8d4c59585f677292d0b84d9a995bd337def3fe6bbe5e6001989b9b6bfe27ea08
+36373781542ab56573248b4c5bc843ac4048c7ab21aa24ca00534c25482828a3
+8c9ee67475bbaaaab22cb722c8e57240a150301a8d219de94e44534d7d90e885
+87acb0e2c4f9800731629b6c5ee14a35a6b9887d2a0032994cb9cf15dbe59650
+ff7b46a04c9a749e7cc5112214266cc65c31354d5b5d5d3d90209bcd5616a552
+a95c2e87f2a659bd9ee01c2cd73964e438f129a6aa9e582c363838b80f81d7eb
+5555b56a2a8ad2d9d7affd0409f8015c208013fea00177b873831b0282c964f2
+783c1e8fa7582cee5f81a669b5e6eeeeaee58e8559b0c233d8843c7c0b963a82
+34e94b5cb2396d7d7d7db22c8ba258fb0afd43f0e2c58b919191ba9de9b4d425
+118329b0c3323c8709d02041b52b4ea7f39de75d2a934a2693c0a953a76a93d4
+5d157ebf7f6565a5542a553df97c5e10045dd731c130b86113cc300cbd489224
+08422a952a140a95788fc763b1d41558d7a2d7af5f5fb870a1d6a3aaaacd6603
+18802da84c59015bd2e6897b745d9765b99a1df0f97c0daf74e36deaf7fbcd66
+73ad2797cb89a2c839880188a2e8743a8bc5a22ccbba5e376466b3b9bdbdbd21
+6123413a9d0e0402b51e4dd3bababa788eb022b85caeb6b6364551b6b7b76942
+43f7f727007a7a7a04a1ee8065b3595fde2768423299ac1ec6669c3973e65004
+c0f8f878ad69341a33994ced2969c0d0d0502412f9f8f163f3a7fd654b474787
+288ad53e74757535df6215b85cae60302849d2410aecc037f9f2e5cbd5b5c160
+680eb0dbede170381c0e7ff8f0a185be3b906068684892a4ca7a6f6faff69328
+8ad3d3d3f7efdfdfdbdbfb57e96868a14d0d0643381c96242997cbe5f3794010
+84603078fcf8f1d6496bd14a3aba5c2ea7d369341a5555b5582c8140e0fcf9f3
+1b1b1b87cf4eeb0a8063c78e45a3d19e9e1ebfdfdf5a831e844655d18093274f
+9e3d7bf6d3a74f3b3b3b47c80efc05ff7af28fefb70d9b0000000049454e44ae
+426082
+"""),
+  'basn6a16': _dehex("""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+"""),
+}
+
+def test_suite(options, args):
+    """
+    Create a PNG test image and write the file to stdout.
+    """
+
+    # Below is a big stack of test image generators.
+    # They're all really tiny, so PEP 8 rules are suspended.
+
+    def test_gradient_horizontal_lr(x, y): return x
+    def test_gradient_horizontal_rl(x, y): return 1-x
+    def test_gradient_vertical_tb(x, y): return y
+    def test_gradient_vertical_bt(x, y): return 1-y
+    def test_radial_tl(x, y): return max(1-math.sqrt(x*x+y*y), 0.0)
+    def test_radial_center(x, y): return test_radial_tl(x-0.5, y-0.5)
+    def test_radial_tr(x, y): return test_radial_tl(1-x, y)
+    def test_radial_bl(x, y): return test_radial_tl(x, 1-y)
+    def test_radial_br(x, y): return test_radial_tl(1-x, 1-y)
+    def test_stripe(x, n): return float(int(x*n) & 1)
+    def test_stripe_h_2(x, y): return test_stripe(x, 2)
+    def test_stripe_h_4(x, y): return test_stripe(x, 4)
+    def test_stripe_h_10(x, y): return test_stripe(x, 10)
+    def test_stripe_v_2(x, y): return test_stripe(y, 2)
+    def test_stripe_v_4(x, y): return test_stripe(y, 4)
+    def test_stripe_v_10(x, y): return test_stripe(y, 10)
+    def test_stripe_lr_10(x, y): return test_stripe(x+y, 10)
+    def test_stripe_rl_10(x, y): return test_stripe(1+x-y, 10)
+    def test_checker(x, y, n): return float((int(x*n) & 1) ^ (int(y*n) & 1))
+    def test_checker_8(x, y): return test_checker(x, y, 8)
+    def test_checker_15(x, y): return test_checker(x, y, 15)
+    def test_zero(x, y): return 0
+    def test_one(x, y): return 1
+
+    test_patterns = {
+        'GLR': test_gradient_horizontal_lr,
+        'GRL': test_gradient_horizontal_rl,
+        'GTB': test_gradient_vertical_tb,
+        'GBT': test_gradient_vertical_bt,
+        'RTL': test_radial_tl,
+        'RTR': test_radial_tr,
+        'RBL': test_radial_bl,
+        'RBR': test_radial_br,
+        'RCTR': test_radial_center,
+        'HS2': test_stripe_h_2,
+        'HS4': test_stripe_h_4,
+        'HS10': test_stripe_h_10,
+        'VS2': test_stripe_v_2,
+        'VS4': test_stripe_v_4,
+        'VS10': test_stripe_v_10,
+        'LRS': test_stripe_lr_10,
+        'RLS': test_stripe_rl_10,
+        'CK8': test_checker_8,
+        'CK15': test_checker_15,
+        'ZERO': test_zero,
+        'ONE': test_one,
+        }
+
+    def test_pattern(width, height, bitdepth, pattern):
+        """Create a single plane (monochrome) test pattern.  Returns a
+        flat row flat pixel array.
+        """
+
+        maxval = 2**bitdepth-1
+        if maxval > 255:
+            a = array('H')
+        else:
+            a = array('B')
+        fw = float(width)
+        fh = float(height)
+        pfun = test_patterns[pattern]
+        for y in range(height):
+            fy = float(y)/fh
+            for x in range(width):
+                a.append(int(round(pfun(float(x)/fw, fy) * maxval)))
+        return a
+
+    def test_rgba(size=256, bitdepth=8,
+                    red="GTB", green="GLR", blue="RTL", alpha=None):
+        """
+        Create a test image.  Each channel is generated from the
+        specified pattern; any channel apart from red can be set to
+        None, which will cause it not to be in the image.  It
+        is possible to create all PNG channel types (L, RGB, LA, RGBA),
+        as well as non PNG channel types (RGA, and so on).
+        """
+
+        i = test_pattern(size, size, bitdepth, red)
+        psize = 1
+        for channel in (green, blue, alpha):
+            if channel:
+                c = test_pattern(size, size, bitdepth, channel)
+                i = interleave_planes(i, c, psize, 1)
+                psize += 1
+        return i
+
+    def pngsuite_image(name):
+        """
+        Create a test image by reading an internal copy of the files
+        from the PngSuite.  Returned in flat row flat pixel format.
+        """
+
+        if name not in _pngsuite:
+            raise NotImplementedError("cannot find PngSuite file %s (use -L for a list)" % name)
+        r = Reader(bytes=_pngsuite[name])
+        w,h,pixels,meta = r.asDirect()
+        assert w == h
+        # LAn for n < 8 is a special case for which we need to rescale
+        # the data.
+        if meta['greyscale'] and meta['alpha'] and meta['bitdepth'] < 8:
+            factor = 255 // (2**meta['bitdepth']-1)
+            def rescale(data):
+                for row in data:
+                    yield map(factor.__mul__, row)
+            pixels = rescale(pixels)
+            meta['bitdepth'] = 8
+        arraycode = 'BH'[meta['bitdepth']>8]
+        return w, array(arraycode, itertools.chain(*pixels)), meta
+
+    # The body of test_suite()
+    size = 256
+    if options.test_size:
+        size = options.test_size
+    options.bitdepth = options.test_depth
+    options.greyscale=bool(options.test_black)
+
+    kwargs = {}
+    if options.test_red:
+        kwargs["red"] = options.test_red
+    if options.test_green:
+        kwargs["green"] = options.test_green
+    if options.test_blue:
+        kwargs["blue"] = options.test_blue
+    if options.test_alpha:
+        kwargs["alpha"] = options.test_alpha
+    if options.greyscale:
+        if options.test_red or options.test_green or options.test_blue:
+            raise ValueError("cannot specify colours (R, G, B) when greyscale image (black channel, K) is specified")
+        kwargs["red"] = options.test_black
+        kwargs["green"] = None
+        kwargs["blue"] = None
+    options.alpha = bool(options.test_alpha)
+    if not args:
+        pixels = test_rgba(size, options.bitdepth, **kwargs)
+    else:
+        size,pixels,meta = pngsuite_image(args[0])
+        for k in ['bitdepth', 'alpha', 'greyscale']:
+            setattr(options, k, meta[k])
+
+    writer = Writer(size, size,
+                    bitdepth=options.bitdepth,
+                    transparent=options.transparent,
+                    background=options.background,
+                    gamma=options.gamma,
+                    greyscale=options.greyscale,
+                    alpha=options.alpha,
+                    compression=options.compression,
+                    interlace=options.interlace)
+    writer.write_array(sys.stdout, pixels)
+
+def read_pam_header(infile):
+    """
+    Read (the rest of a) PAM header.  `infile` should be positioned
+    immediately after the initial 'P7' line (at the beginning of the
+    second line).  Returns are as for `read_pnm_header`.
+    """
+    
+    # Unlike PBM, PGM, and PPM, we can read the header a line at a time.
+    header = dict()
+    while True:
+        l = infile.readline().strip()
+        if l == strtobytes('ENDHDR'):
+            break
+        if not l:
+            raise EOFError('PAM ended prematurely')
+        if l[0] == strtobytes('#'):
+            continue
+        l = l.split(None, 1)
+        if l[0] not in header:
+            header[l[0]] = l[1]
+        else:
+            header[l[0]] += strtobytes(' ') + l[1]
+
+    required = ['WIDTH', 'HEIGHT', 'DEPTH', 'MAXVAL']
+    required = [strtobytes(x) for x in required]
+    WIDTH,HEIGHT,DEPTH,MAXVAL = required
+    present = [x for x in required if x in header]
+    if len(present) != len(required):
+        raise Error('PAM file must specify WIDTH, HEIGHT, DEPTH, and MAXVAL')
+    width = int(header[WIDTH])
+    height = int(header[HEIGHT])
+    depth = int(header[DEPTH])
+    maxval = int(header[MAXVAL])
+    if (width <= 0 or
+        height <= 0 or
+        depth <= 0 or
+        maxval <= 0):
+        raise Error(
+          'WIDTH, HEIGHT, DEPTH, MAXVAL must all be positive integers')
+    return 'P7', width, height, depth, maxval
+
+def read_pnm_header(infile, supported=('P5','P6')):
+    """
+    Read a PNM header, returning (format,width,height,depth,maxval).
+    `width` and `height` are in pixels.  `depth` is the number of
+    channels in the image; for PBM and PGM it is synthesized as 1, for
+    PPM as 3; for PAM images it is read from the header.  `maxval` is
+    synthesized (as 1) for PBM images.
+    """
+
+    # Generally, see http://netpbm.sourceforge.net/doc/ppm.html
+    # and http://netpbm.sourceforge.net/doc/pam.html
+
+    supported = [strtobytes(x) for x in supported]
+
+    # Technically 'P7' must be followed by a newline, so by using
+    # rstrip() we are being liberal in what we accept.  I think this
+    # is acceptable.
+    type = infile.read(3).rstrip()
+    if type not in supported:
+        raise NotImplementedError('file format %s not supported' % type)
+    if type == strtobytes('P7'):
+        # PAM header parsing is completely different.
+        return read_pam_header(infile)
+    # Expected number of tokens in header (3 for P4, 4 for P6)
+    expected = 4
+    pbm = ('P1', 'P4')
+    if type in pbm:
+        expected = 3
+    header = [type]
+
+    # We have to read the rest of the header byte by byte because the
+    # final whitespace character (immediately following the MAXVAL in
+    # the case of P6) may not be a newline.  Of course all PNM files in
+    # the wild use a newline at this point, so it's tempting to use
+    # readline; but it would be wrong.
+    def getc():
+        c = infile.read(1)
+        if not c:
+            raise Error('premature EOF reading PNM header')
+        return c
+
+    c = getc()
+    while True:
+        # Skip whitespace that precedes a token.
+        while c.isspace():
+            c = getc()
+        # Skip comments.
+        while c == '#':
+            while c not in '\n\r':
+                c = getc()
+        if not c.isdigit():
+            raise Error('unexpected character %s found in header' % c)
+        # According to the specification it is legal to have comments
+        # that appear in the middle of a token.
+        # This is bonkers; I've never seen it; and it's a bit awkward to
+        # code good lexers in Python (no goto).  So we break on such
+        # cases.
+        token = strtobytes('')
+        while c.isdigit():
+            token += c
+            c = getc()
+        # Slight hack.  All "tokens" are decimal integers, so convert
+        # them here.
+        header.append(int(token))
+        if len(header) == expected:
+            break
+    # Skip comments (again)
+    while c == '#':
+        while c not in '\n\r':
+            c = getc()
+    if not c.isspace():
+        raise Error('expected header to end with whitespace, not %s' % c)
+
+    if type in pbm:
+        # synthesize a MAXVAL
+        header.append(1)
+    depth = (1,3)[type == strtobytes('P6')]
+    return header[0], header[1], header[2], depth, header[3]
+
+def write_pnm(file, width, height, pixels, meta):
+    """Write a Netpbm PNM/PAM file."""
+
+    bitdepth = meta['bitdepth']
+    maxval = 2**bitdepth - 1
+    # Rudely, the number of image planes can be used to determine
+    # whether we are L (PGM), LA (PAM), RGB (PPM), or RGBA (PAM).
+    planes = meta['planes']
+    # Can be an assert as long as we assume that pixels and meta came
+    # from a PNG file.
+    assert planes in (1,2,3,4)
+    if planes in (1,3):
+        if 1 == planes:
+            # PGM
+            # Could generate PBM if maxval is 1, but we don't (for one
+            # thing, we'd have to convert the data, not just blat it
+            # out).
+            fmt = 'P5'
+        else:
+            # PPM
+            fmt = 'P6'
+        file.write('%s %d %d %d\n' % (fmt, width, height, maxval))
+    if planes in (2,4):
+        # PAM
+        # See http://netpbm.sourceforge.net/doc/pam.html
+        if 2 == planes:
+            tupltype = 'GRAYSCALE_ALPHA'
+        else:
+            tupltype = 'RGB_ALPHA'
+        file.write('P7\nWIDTH %d\nHEIGHT %d\nDEPTH %d\nMAXVAL %d\n'
+                   'TUPLTYPE %s\nENDHDR\n' %
+                   (width, height, planes, maxval, tupltype))
+    # Values per row
+    vpr = planes * width
+    # struct format
+    fmt = '>%d' % vpr
+    if maxval > 0xff:
+        fmt = fmt + 'H'
+    else:
+        fmt = fmt + 'B'
+    for row in pixels:
+        file.write(struct.pack(fmt, *row))
+    file.flush()
+
+def color_triple(color):
+    """
+    Convert a command line colour value to a RGB triple of integers.
+    FIXME: Somewhere we need support for greyscale backgrounds etc.
+    """
+    if color.startswith('#') and len(color) == 4:
+        return (int(color[1], 16),
+                int(color[2], 16),
+                int(color[3], 16))
+    if color.startswith('#') and len(color) == 7:
+        return (int(color[1:3], 16),
+                int(color[3:5], 16),
+                int(color[5:7], 16))
+    elif color.startswith('#') and len(color) == 13:
+        return (int(color[1:5], 16),
+                int(color[5:9], 16),
+                int(color[9:13], 16))
+
+
+def _main(argv):
+    """
+    Run the PNG encoder with options from the command line.
+    """
+
+    # Parse command line arguments
+    from optparse import OptionParser
+    import re
+    version = '%prog ' + re.sub(r'( ?\$|URL: |Rev:)', '', __version__)
+    parser = OptionParser(version=version)
+    parser.set_usage("%prog [options] [imagefile]")
+    parser.add_option('-r', '--read-png', default=False,
+                      action='store_true',
+                      help='Read PNG, write PNM')
+    parser.add_option("-i", "--interlace",
+                      default=False, action="store_true",
+                      help="create an interlaced PNG file (Adam7)")
+    parser.add_option("-t", "--transparent",
+                      action="store", type="string", metavar="color",
+                      help="mark the specified colour (#RRGGBB) as transparent")
+    parser.add_option("-b", "--background",
+                      action="store", type="string", metavar="color",
+                      help="save the specified background colour")
+    parser.add_option("-a", "--alpha",
+                      action="store", type="string", metavar="pgmfile",
+                      help="alpha channel transparency (RGBA)")
+    parser.add_option("-g", "--gamma",
+                      action="store", type="float", metavar="value",
+                      help="save the specified gamma value")
+    parser.add_option("-c", "--compression",
+                      action="store", type="int", metavar="level",
+                      help="zlib compression level (0-9)")
+    parser.add_option("-T", "--test",
+                      default=False, action="store_true",
+                      help="create a test image (a named PngSuite image if an argument is supplied)")
+    parser.add_option('-L', '--list',
+                      default=False, action='store_true',
+                      help="print list of named test images")
+    parser.add_option("-R", "--test-red",
+                      action="store", type="string", metavar="pattern",
+                      help="test pattern for the red image layer")
+    parser.add_option("-G", "--test-green",
+                      action="store", type="string", metavar="pattern",
+                      help="test pattern for the green image layer")
+    parser.add_option("-B", "--test-blue",
+                      action="store", type="string", metavar="pattern",
+                      help="test pattern for the blue image layer")
+    parser.add_option("-A", "--test-alpha",
+                      action="store", type="string", metavar="pattern",
+                      help="test pattern for the alpha image layer")
+    parser.add_option("-K", "--test-black",
+                      action="store", type="string", metavar="pattern",
+                      help="test pattern for greyscale image")
+    parser.add_option("-d", "--test-depth",
+                      default=8, action="store", type="int",
+                      metavar='NBITS',
+                      help="create test PNGs that are NBITS bits per channel")
+    parser.add_option("-S", "--test-size",
+                      action="store", type="int", metavar="size",
+                      help="width and height of the test image")
+    (options, args) = parser.parse_args(args=argv[1:])
+
+    # Convert options
+    if options.transparent is not None:
+        options.transparent = color_triple(options.transparent)
+    if options.background is not None:
+        options.background = color_triple(options.background)
+
+    if options.list:
+        names = list(_pngsuite)
+        names.sort()
+        for name in names:
+            print name
+        return
+
+    # Run regression tests
+    if options.test:
+        return test_suite(options, args)
+
+    # Prepare input and output files
+    if len(args) == 0:
+        infilename = '-'
+        infile = sys.stdin
+    elif len(args) == 1:
+        infilename = args[0]
+        infile = open(infilename, 'rb')
+    else:
+        parser.error("more than one input file")
+    outfile = sys.stdout
+
+    if options.read_png:
+        # Encode PNG to PPM
+        png = Reader(file=infile)
+        width,height,pixels,meta = png.asDirect()
+        write_pnm(outfile, width, height, pixels, meta) 
+    else:
+        # Encode PNM to PNG
+        format, width, height, depth, maxval = \
+          read_pnm_header(infile, ('P5','P6','P7'))
+        # When it comes to the variety of input formats, we do something
+        # rather rude.  Observe that L, LA, RGB, RGBA are the 4 colour
+        # types supported by PNG and that they correspond to 1, 2, 3, 4
+        # channels respectively.  So we use the number of channels in
+        # the source image to determine which one we have.  We do not
+        # care about TUPLTYPE.
+        greyscale = depth <= 2
+        pamalpha = depth in (2,4)
+        supported = map(lambda x: 2**x-1, range(1,17))
+        try:
+            mi = supported.index(maxval)
+        except ValueError:
+            raise NotImplementedError(
+              'your maxval (%s) not in supported list %s' %
+              (maxval, str(supported)))
+        bitdepth = mi+1
+        writer = Writer(width, height,
+                        greyscale=greyscale,
+                        bitdepth=bitdepth,
+                        interlace=options.interlace,
+                        transparent=options.transparent,
+                        background=options.background,
+                        alpha=bool(pamalpha or options.alpha),
+                        gamma=options.gamma,
+                        compression=options.compression)
+        if options.alpha:
+            pgmfile = open(options.alpha, 'rb')
+            format, awidth, aheight, adepth, amaxval = \
+              read_pnm_header(pgmfile, 'P5')
+            if amaxval != '255':
+                raise NotImplementedError(
+                  'maxval %s not supported for alpha channel' % amaxval)
+            if (awidth, aheight) != (width, height):
+                raise ValueError("alpha channel image size mismatch"
+                                 " (%s has %sx%s but %s has %sx%s)"
+                                 % (infilename, width, height,
+                                    options.alpha, awidth, aheight))
+            writer.convert_ppm_and_pgm(infile, pgmfile, outfile)
+        else:
+            writer.convert_pnm(infile, outfile)
+
+
+if __name__ == '__main__':
+    try:
+        _main(sys.argv)
+    except Error, e:
+        print >>sys.stderr, e
new file mode 100644
--- /dev/null
+++ b/build/pypng/pngchunk
@@ -0,0 +1,172 @@
+#!/usr/bin/env python
+# $URL: http://pypng.googlecode.com/svn/trunk/code/pngchunk $
+# $Rev: 156 $
+# pngchunk
+# Chunk editing/extraction tool.
+
+import struct
+import warnings
+
+# Local module.
+import png
+
+"""
+pngchunk [--gamma g] [--iccprofile file] [--sigbit b] [-c cHNK!] [-c cHNK:foo] [-c cHNK<file]
+
+The ``-c`` option is used to add or remove chunks.  A chunk is specified
+by its 4 byte chunk type.  If this is followed by a ``!`` then that
+chunk is removed from the PNG file.  If the chunk type is followed by a
+``:`` then the chunk is replaced with the contents of the rest of the
+argument (this is probably only useful if the content is mostly ASCII,
+otherwise it's a pain to quote the contents, otherwise see...).  A ``<``
+can be used to take the contents of the chunk from the named file.
+"""
+
+
+def chunk(out, inp, l):
+    """Process the input PNG file to the output, chunk by chunk.  Chunks
+    can be inserted, removed, replaced, or sometimes edited.  Generally, 
+    chunks are not inspected, so pixel data (in the ``IDAT`` chunks)
+    cannot be modified.  `l` should be a list of (*chunktype*,
+    *content*) pairs.  *chunktype* is usually the type of the PNG chunk,
+    specified as a 4-byte Python string, and *content* is the chunk's
+    content, also as a string; if *content* is ``None`` then *all*
+    chunks of that type will be removed.
+
+    This function *knows* about certain chunk types and will
+    automatically convert from Python friendly representations to
+    string-of-bytes.
+
+    chunktype
+    'gamma'     'gAMA'  float
+    'sigbit'    'sBIT'  int, or tuple of length 1,2 or 3
+
+    Note that the length of the strings used to identify *friendly*
+    chunk types is greater than 4, hence they cannot be confused with
+    canonical chunk types.
+
+    Chunk types, if specified using the 4-byte syntax, need not be
+    official PNG chunks at all.  Non-standard chunks can be created.
+    """
+
+    def canonical(p):
+        """Take a pair (*chunktype*, *content*), and return canonical
+        representation (*chunktype*, *content*) where `chunktype` is the
+        4-byte PNG chunk type and `content` is a string.
+        """
+
+        t,v = p
+        if len(t) == 4:
+            return t,v
+        if t == 'gamma':
+            t = 'gAMA'
+            v = int(round(1e5*v))
+            v = struct.pack('>I', v)
+        elif t == 'sigbit':
+            t = 'sBIT'
+            try:
+                v[0]
+            except TypeError:
+                v = (v,)
+            v = struct.pack('%dB' % len(v), *v)
+        elif t == 'iccprofile':
+            t = 'iCCP'
+            # http://www.w3.org/TR/PNG/#11iCCP
+            v = 'a color profile\x00\x00' + v.encode('zip')
+        else:
+            warnings.warn('Unknown chunk type %r' % t)
+        return t[:4],v
+
+    l = map(canonical, l)
+    # Some chunks automagically replace ones that are present in the
+    # source PNG.  There can only be one of each of these chunk types.
+    # Create a 'replace' dictionary to record these chunks.
+    add = []
+    delete = set()
+    replacing = set(['gAMA', 'sBIT', 'PLTE', 'tRNS', 'sPLT', 'IHDR'])
+    replace = dict()
+    for t,v in l:
+        if v is None:
+            delete.add(t)
+        elif t in replacing:
+            replace[t] = v
+        else:
+            add.append((t,v))
+    del l
+    r = png.Reader(file=inp)
+    chunks = r.chunks()
+    def iterchunks():
+        for t,v in chunks:
+            if t in delete:
+                continue
+            if t in replace:
+                yield t,replace[t]
+                del replace[t]
+                continue
+            if t == 'IDAT' and replace:
+                # Insert into the output any chunks that are on the
+                # replace list.  We haven't output them yet, because we
+                # didn't see an original chunk of the same type to
+                # replace.  Thus the "replace" is actually an "insert".
+                for u,w in replace.items():
+                    yield u,w
+                    del replace[u]
+            if t == 'IDAT' and add:
+                for item in add:
+                    yield item
+                del add[:]
+            yield t,v
+    return png.write_chunks(out, iterchunks())
+
+class Usage(Exception):
+    pass
+
+def main(argv=None):
+    import getopt
+    import re
+    import sys
+
+    if argv is None:
+        argv = sys.argv
+
+    argv = argv[1:]
+
+    try:
+        try:
+            opt,arg = getopt.getopt(argv, 'c:',
+                                    ['gamma=', 'iccprofile=', 'sigbit='])
+        except getopt.error, msg:
+            raise Usage(msg)
+        k = []
+        for o,v in opt:
+            if o in ['--gamma']:
+                k.append(('gamma', float(v)))
+            if o in ['--sigbit']:
+                k.append(('sigbit', int(v)))
+            if o in ['--iccprofile']:
+                k.append(('iccprofile', open(v, 'rb').read()))
+            if o in ['-c']:
+                type = v[:4]
+                if not re.match('[a-zA-Z]{4}', type):
+                    raise Usage('Chunk type must consist of 4 letters.')
+                if v[4] == '!':
+                    k.append((type, None))
+                if v[4] == ':':
+                    k.append((type, v[5:]))
+                if v[4] == '<':
+                    k.append((type, open(v[5:], 'rb').read()))
+    except Usage, err:
+        print >>sys.stderr, (
+          "usage: pngchunk [--gamma d.dd] [--sigbit b] [-c cHNK! | -c cHNK:text-string]")
+        print >>sys.stderr, err.message
+        return 2
+
+    if len(arg) > 0:
+        f = open(arg[0], 'rb')
+    else:
+        f = sys.stdin
+    return chunk(sys.stdout, f, k)
+
+
+if __name__ == '__main__':
+    main()
new file mode 100644
--- /dev/null
+++ b/build/pypng/pnghist
@@ -0,0 +1,79 @@
+#!/usr/bin/env python
+# $URL: http://pypng.googlecode.com/svn/trunk/code/pnghist $
+# $Rev: 153 $
+# PNG Histogram
+# Only really works on grayscale images.
+
+from array import array
+import getopt
+
+import png
+
+def decidemax(level):
+    """Given an array of levels, decide the maximum value to use for the
+    histogram.  This is normally chosen to be a bit bigger than the 99th
+    percentile, but if the 100th percentile is not much more (within a
+    factor of 2) then the 100th percentile is chosen.
+    """
+
+    truemax = max(level)
+    sl = level[:]
+    sl.sort(reverse=True)
+    i99 = int(round(len(level)*0.01))
+    if truemax <= 2*sl[i99]:
+        return truemax
+    return 1.05*sl[i99]
+
+def hist(out, inp, verbose=None):
+    """Open the PNG file `inp` and generate a histogram."""
+
+    r = png.Reader(file=inp)
+    x,y,pixels,info = r.asDirect()
+    bitdepth = info['bitdepth']
+    level = [0]*2**bitdepth
+    for row in pixels:
+        for v in row:
+            level[v] += 1
+    maxlevel = decidemax(level)
+
+    h = 100
+    outbitdepth = 8
+    outmaxval = 2**outbitdepth - 1
+    def genrow():
+        for y in range(h):
+            y = h-y-1
+            # :todo: vary typecode according to outbitdepth
+            row = array('B', [0]*len(level))
+            fl = y*maxlevel/float(h)
+            ce = (y+1)*maxlevel/float(h)
+            for x in range(len(row)):
+                if level[x] <= fl:
+                    # Relies on row being initialised to all 0
+                    continue
+                if level[x] >= ce:
+                    row[x] = outmaxval
+                    continue
+                frac = (level[x] - fl)/(ce - fl)
+                row[x] = int(round(outmaxval*frac))
+            yield row
+    w = png.Writer(len(level), h, gamma=1.0,
+      greyscale=True, alpha=False, bitdepth=outbitdepth)
+    w.write(out, genrow())
+    if verbose: print >>verbose, level
+
+def main(argv=None):
+    import sys
+
+    if argv is None:
+        argv = sys.argv
+    argv = argv[1:]
+    opt,arg = getopt.getopt(argv, '')
+
+    if len(arg) < 1:
+        f = sys.stdin
+    else:
+        f = open(arg[0])
+    hist(sys.stdout, f)
+
+if __name__ == '__main__':
+    main()
new file mode 100644
--- /dev/null
+++ b/build/pypng/pnglsch
@@ -0,0 +1,31 @@
+#!/usr/bin/env python
+# $URL: http://pypng.googlecode.com/svn/trunk/code/pnglsch $
+# $Rev: 107 $
+# pnglsch
+# PNG List Chunks
+
+import png
+
+def list(out, inp):
+    r = png.Reader(file=inp)
+    for t,v in r.chunks():
+        add = ''
+        if len(v) <= 28:
+            add = ' ' + v.encode('hex')
+        print >>out, "%s %10d%s" % (t, len(v), add)
+
+def main(argv=None):
+    import sys
+
+    if argv is None:
+        argv = sys.argv
+    arg = argv[1:]
+
+    if len(arg) > 0:
+        f = open(arg[0], 'rb')
+    else:
+        f = sys.stdin
+    return list(sys.stdout, f)
+
+if __name__ == '__main__':
+    main()
new file mode 100644
--- /dev/null
+++ b/build/pypng/texttopng
@@ -0,0 +1,151 @@
+#!/usr/bin/env python
+# $URL: http://pypng.googlecode.com/svn/trunk/code/texttopng $
+# $Rev: 132 $
+# Script to renders text as a PNG image.
+
+from array import array
+import itertools
+
+font = {
+  32: '0000000000000000',
+  33: '0010101010001000',
+  34: '0028280000000000',
+  35: '0000287c287c2800',
+  36: '00103c5038147810',
+  37: '0000644810244c00',
+  38: '0020502054483400',
+  39: '0010100000000000',
+  40: '0008101010101008',
+  41: '0020101010101020',
+  42: '0010543838541000',
+  43: '000010107c101000',
+  44: '0000000000301020',
+  45: '000000007c000000',
+  46: '0000000000303000',
+  47: '0000040810204000',
+  48: '0038445454443800',
+  49: '0008180808080800',
+  50: '0038043840407c00',
+  51: '003c041804043800',
+  52: '00081828487c0800',
+  53: '0078407804047800',
+  54: '0038407844443800',
+  55: '007c040810101000',
+  56: '0038443844443800',
+  57: '0038443c04040400',
+  58: '0000303000303000',
+  59: '0000303000301020',
+  60: '0004081020100804',
+  61: '0000007c007c0000',
+  62: '0040201008102040',
+  63: '0038440810001000',
+  64: '00384c545c403800',
+  65: '0038447c44444400',
+  66: '0078447844447800',
+  67: '0038444040443800',
+  68: '0070484444487000',
+  69: '007c407840407c00',
+  70: '007c407840404000',
+  71: '003844405c443c00',
+  72: '0044447c44444400',
+  73: '0038101010103800',
+  74: '003c040404443800',
+  75: '0044487048444400',
+  76: '0040404040407c00',
+  77: '006c545444444400',
+  78: '004464544c444400',
+  79: '0038444444443800',
+  80: '0078447840404000',
+  81: '0038444444443c02',
+  82: '0078447844444400',
+  83: '0038403804047800',
+  84: '007c101010101000',
+  85: '0044444444443c00',
+  86: '0044444444281000',
+  87: '0044445454543800',
+  88: '0042241818244200',
+  89: '0044443810101000',
+  90: '007c081020407c00',
+  91: '0038202020202038',
+  92: '0000402010080400',
+  93: '0038080808080838',
+  94: '0010284400000000',
+  95: '000000000000fe00',
+  96: '0040200000000000',
+  97: '000038043c443c00',
+  98: '0040784444447800',
+  99: '0000384040403800',
+  100: '00043c4444443c00',
+  101: '000038447c403c00',
+  102: '0018203820202000',
+  103: '00003c44443c0438',
+  104: '0040784444444400',
+  105: '0010003010101000',
+  106: '0010003010101020',
+  107: '0040404870484400',
+  108: '0030101010101000',
+  109: '0000385454444400',
+  110: '0000784444444400',
+  111: '0000384444443800',
+  112: '0000784444784040',
+  113: '00003c44443c0406',
+  114: '00001c2020202000',
+  115: '00003c4038047800',
+  116: '0020203820201800',
+  117: '0000444444443c00',
+  118: '0000444444281000',
+  119: '0000444454543800',
+  120: '0000442810284400',
+  121: '00004444443c0438',
+  122: '00007c0810207c00',
+  123: '0018202060202018',
+  124: '0010101000101010',
+  125: '003008080c080830',
+  126: '0020540800000000',
+}
+
+def char(i):
+    """Get image data for the character `i` (a one character string).
+    Returned as a list of rows.  Each row is a tuple containing the
+    packed pixels.
+    """
+
+    i = ord(i)
+    if i not in font:
+        return [(0,)]*8
+    return map(lambda row: (ord(row),), font[i].decode('hex'))
+
+def texttoraster(m):
+    """Convert string *m* to a raster image (by rendering it using the
+    font in *font*).  A triple of (*width*, *height*, *pixels*) is
+    returned; *pixels* is in boxed row packed pixel format.
+    """
+
+    # Assumes monospaced font.
+    x = 8*len(m)
+    y = 8
+    return x,y,itertools.imap(lambda row: itertools.chain(*row),
+                              zip(*map(char, m)))
+
+
+def render(message, out):
+    import png
+
+    x,y,pixels = texttoraster(message)
+    w = png.Writer(x, y, greyscale=True, bitdepth=1)
+    w.write_packed(out, pixels)
+    out.flush()
+
+def main(argv=None):
+    import sys
+
+    if argv is None:
+        argv = sys.argv
+    if len(argv) > 1:
+        message = argv[1]
+    else:
+        message = sys.stdin.read()
+    render(message, sys.stdout)
+
+if __name__ == '__main__':
+    main()
--- a/config/config.mk
+++ b/config/config.mk
@@ -647,16 +647,21 @@ DIR_INSTALL = $(INSTALL)
 endif # WINNT
 
 ifeq ($(OS_ARCH),WINNT)
 ifneq (,$(CYGDRIVE_MOUNT))
 export CYGDRIVE_MOUNT
 endif
 endif
 
+# png to ico converter. The function takes 5 arguments, in order: source png
+# file, left, top, size, output ico file.
+png2ico = $(PYTHON) $(MOZILLA_DIR)/config/pythonpath.py \
+  -I$(topsrcdir)/build/pypng $(topsrcdir)/build/png2ico.py $(1) $(2) $(3) $(4) $(5)
+
 #
 # Localization build automation
 #
 
 # Because you might wish to "make locales AB_CD=ab-CD", we don't hardcode
 # MOZ_UI_LOCALE directly, but use an intermediate variable that can be
 # overridden by the command line. (Besides, AB_CD is prettier).
 AB_CD = $(MOZ_UI_LOCALE)
--- a/mail/app/Makefile.in
+++ b/mail/app/Makefile.in
@@ -138,16 +138,26 @@ include $(topsrcdir)/config/config.mk
 
 ifdef _MSC_VER
 # Always enter a Windows program through wmain, whether or not we're
 # a console application.
 WIN32_EXE_LDFLAGS += -ENTRY:wmainCRTStartup
 endif
 
 ifeq ($(OS_ARCH),WINNT)
+# Extract the icons we care about embedding into the EXE
+mailtoolbar = $(topsrcdir)/mail/themes/qute/mail/icons/mail-toolbar-aero.png
+# Each icon is 18x18 in the toolbar, and we want a 16x16 icon here, so we cut
+# off a pixel at each end.
+libs::
+	$(call png2ico,$(mailtoolbar),19,1,16,write-message.ico)
+	$(call png2ico,$(mailtoolbar),37,1,16,address-book.ico)
+
+GARBAGE += write-message.ico address-book.ico
+
 OS_LIBS += $(call EXPAND_LIBNAME,comctl32 comdlg32 uuid shell32 ole32 oleaut32 version winspool)
 OS_LIBS += $(call EXPAND_LIBNAME,usp10 msimg32)
 RCINCLUDE = splash.rc
 ifndef GNU_CC
 RCFLAGS += -DMOZ_THUNDERBIRD -I$(srcdir)
 else
 RCFLAGS += -DMOZ_THUNDERBIRD --include-dir $(srcdir)
 endif
--- a/mail/app/splash.rc
+++ b/mail/app/splash.rc
@@ -78,15 +78,20 @@ IDC_ZOOMIN              CURSOR  DISCARDA
 IDC_ZOOMOUT             CURSOR  DISCARDABLE     "../../mozilla/widget/src/build/res/zoom_out.cur"
 IDC_COLRESIZE           CURSOR  DISCARDABLE     "../../mozilla/widget/src/build/res/col_resize.cur"
 IDC_ROWRESIZE           CURSOR  DISCARDABLE     "../../mozilla/widget/src/build/res/row_resize.cur"
 IDC_VERTICALTEXT        CURSOR  DISCARDABLE     "../../mozilla/widget/src/build/res/vertical_text.cur"
 IDC_NONE                CURSOR  DISCARDABLE     "../../mozilla/widget/src/build/res/none.cur"
 
 #endif
 
-// For some reason IDI_MAILBIFF needs to be larger than the value of IDI_APPLICATION for static builds
-#define IDI_MAILBIFF 32767
-IDI_MAILBIFF  ICON  "../../mailnews/build/newmail.ico"
-
 // Program icon.
 IDI_APPLICATION ICON THUNDERBIRD_ICO
 
+// For some reason IDI_MAILBIFF needs to be larger than the value of IDI_APPLICATION for static builds
+#define IDI_MAILBIFF 32576
+IDI_MAILBIFF  ICON  "../../mailnews/build/newmail.ico"
+
+// Windows taskbar icons
+#define IDI_WRITE_MESSAGE 32577
+#define IDI_ADDRESS_BOOK  32578
+IDI_WRITE_MESSAGE ICON "write-message.ico"
+IDI_ADDRESS_BOOK  ICON "address-book.ico"
--- a/mail/components/wintaskbar/windowsJumpLists.js
+++ b/mail/components/wintaskbar/windowsJumpLists.js
@@ -78,25 +78,25 @@ function _getString(aName) {
  * Task list
  */
 let gTasks = [
   // Write new message
   {
     get title()       _getString("taskbar.tasks.composeMessage.label"),
     get description() _getString("taskbar.tasks.composeMessage.description"),
     args:             "-compose",
-    iconIndex:        0, // Tb app icon
+    iconIndex:        2, // Write message icon
   },
 
   // Open address book
   {
     get title()       _getString("taskbar.tasks.openAddressBook.label"),
     get description() _getString("taskbar.tasks.openAddressBook.description"),
     args:             "-addressbook",
-    iconIndex:        0, // Tb app icon
+    iconIndex:        3, // Open address book icon
   },
 ];
 
 
 let WinTaskbarJumpList = {
 
   /**
    * Startup, shutdown, and update
--- a/mailnews/base/src/nsMessengerWinIntegration.cpp
+++ b/mailnews/base/src/nsMessengerWinIntegration.cpp
@@ -84,17 +84,17 @@
 
 #define XP_SHSetUnreadMailCounts "SHSetUnreadMailCountW"
 #define XP_SHEnumerateUnreadMailAccounts "SHEnumerateUnreadMailAccountsW"
 #define NOTIFICATIONCLASSNAME "MailBiffNotificationMessageWindow"
 #define UNREADMAILNODEKEY "Software\\Microsoft\\Windows\\CurrentVersion\\UnreadMail\\"
 #define SHELL32_DLL NS_LITERAL_CSTRING("shell32.dll")
 #define DOUBLE_QUOTE "\""
 #define MAIL_COMMANDLINE_ARG " -mail"
-#define IDI_MAILBIFF 32767
+#define IDI_MAILBIFF 32576
 #define UNREAD_UPDATE_INTERVAL	(20 * 1000)	// 20 seconds
 #define ALERT_CHROME_URL "chrome://messenger/content/newmailalert.xul"
 #define NEW_MAIL_ALERT_ICON "chrome://messenger/skin/icons/new-mail-alert.png"
 #define SHOW_ALERT_PREF     "mail.biff.show_alert"
 #define SHOW_TRAY_ICON_PREF "mail.biff.show_tray_icon"
 #define SHOW_BALLOON_PREF   "mail.biff.show_balloon"
 
 // since we are including windows.h in this file, undefine get user name....
--- a/suite/app/splash.rc
+++ b/suite/app/splash.rc
@@ -74,14 +74,14 @@ IDC_ZOOMIN              CURSOR  DISCARDA
 IDC_ZOOMOUT             CURSOR  DISCARDABLE     "../../mozilla/widget/src/build/res/zoom_out.cur"
 IDC_COLRESIZE           CURSOR  DISCARDABLE     "../../mozilla/widget/src/build/res/col_resize.cur"
 IDC_ROWRESIZE           CURSOR  DISCARDABLE     "../../mozilla/widget/src/build/res/row_resize.cur"
 IDC_VERTICALTEXT        CURSOR  DISCARDABLE     "../../mozilla/widget/src/build/res/vertical_text.cur"
 IDC_NONE                CURSOR  DISCARDABLE     "../../mozilla/widget/src/build/res/none.cur"
 
 #endif
 
-// For some reason IDI_MAILBIFF needs to be larger than the value of IDI_APPLICATION for static builds
-#define IDI_MAILBIFF 32767
-IDI_MAILBIFF  ICON  "../../mailnews/build/newmail.ico"
-
 // Program icon.
 IDI_APPLICATION ICON SEAMONKEY_ICO
+
+// For some reason IDI_MAILBIFF needs to be larger than the value of IDI_APPLICATION for static builds
+#define IDI_MAILBIFF 32576
+IDI_MAILBIFF  ICON  "../../mailnews/build/newmail.ico"