author Brian R. Bondy <>
Thu, 25 Aug 2011 16:09:01 -0400
changeset 75917 1f86f6af9434b4d9afe3eb0998f7f9f8c1149ac3
parent 53665 817a480e3836d07cb9a5966f656ac593477a14de
child 75919 52f2d362cbac1a65d099fb363a2ea8efc2d76394
permissions -rw-r--r--
Bug 600556 - Support Vista-style PNG ICO files. r=joe

/* vim:set tw=80 expandtab softtabstop=4 ts=4 sw=4: */
/* ***** 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
 * 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 the Mozilla BMP Decoder.
 * The Initial Developer of the Original Code is
 * Christian Biesinger <>.
 * Portions created by the Initial Developer are Copyright (C) 2001
 * the Initial Developer. All Rights Reserved.
 * Contributor(s):
 *   Bobby Holley <>
 *   Brian R. Bondy <>
 * 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 ***** */

#ifndef _nsBMPDecoder_h
#define _nsBMPDecoder_h

#include "nsAutoPtr.h"
#include "imgIDecoderObserver.h"
#include "gfxColor.h"
#include "Decoder.h"

namespace mozilla {
namespace imagelib {

    char signature[2]; // String "BM"
    PRUint32 filesize;
    PRInt32 reserved; // Zero
    PRUint32 dataoffset; // Offset to raster data

    PRUint32 bihsize;

// The length of the bitmap file header as defined in the BMP spec.
#define BFH_LENGTH 14 
// Internally we store the bitmap file header with an additional 4 bytes which
// is used to store the bitmap information header size.

#define OS2_BIH_LENGTH 12 // This is the real BIH size (as contained in the bihsize field of BMPFILEHEADER)

    PRInt32 width; // Uint16 in OS/2 BMPs
    PRInt32 height; // Uint16 in OS/2 BMPs
    PRUint16 planes; // =1
    PRUint16 bpp; // Bits per pixel.
    // The rest of the header is not available in OS/2 BMP Files
    PRUint32 compression; // 0=no compression 1=8bit RLE 2=4bit RLE
    PRUint32 image_size; // (compressed) image size. Can be 0 if compression==0
    PRUint32 xppm; // Pixels per meter, horizontal
    PRUint32 yppm; // Pixels per meter, vertical
    PRUint32 colors; // Used Colors
    PRUint32 important_colors; // Number of important colors. 0=all

struct colorTable {
    PRUint8 red;
    PRUint8 green;
    PRUint8 blue;

struct bitFields {
    PRUint32 red;
    PRUint32 green;
    PRUint32 blue;
    PRUint8 redLeftShift;
    PRUint8 redRightShift;
    PRUint8 greenLeftShift;
    PRUint8 greenRightShift;
    PRUint8 blueLeftShift;
    PRUint8 blueRightShift;

#define BITFIELD_LENGTH 12 // Length of the bitfields structure in the bmp file

#if defined WORDS_BIGENDIAN || defined IS_BIG_ENDIAN
// We must ensure that the entity is unsigned
// otherwise, if it is signed/negative, the MSB will be
// propagated when we shift
#define LITTLE_TO_NATIVE16(x) (((((PRUint16) x) & 0xFF) << 8) | \
                               (((PRUint16) x) >> 8))
#define LITTLE_TO_NATIVE32(x) (((((PRUint32) x) & 0xFF) << 24) | \
                               (((((PRUint32) x) >> 8) & 0xFF) << 16) | \
                               (((((PRUint32) x) >> 16) & 0xFF) << 8) | \
                               (((PRUint32) x) >> 24))


#define LITTLE_TO_NATIVE16(x) x
#define LITTLE_TO_NATIVE32(x) x
#define NATIVE32_TO_LITTLE(x) x


#define USE_RGB

// BMPINFOHEADER.compression defines
#ifndef BI_RGB
#define BI_RGB 0
#ifndef BI_RLE8
#define BI_RLE8 1
#ifndef BI_RLE4
#define BI_RLE4 2
#define BI_BITFIELDS 3
// BI_ALPHABITFIELDS  means no compression and specifies alpha bits
// valid only for 32bpp and 16bpp

// RLE Escape codes
#define RLE_ESCAPE       0
#define RLE_ESCAPE_EOL   0
#define RLE_ESCAPE_EOF   1

/// enums for mState
enum ERLEState {
    eRLEStateNeedYDelta,    ///< mStateData will hold x delta
    eRLEStateAbsoluteMode,  ///< mStateData will hold count of existing data to read
    eRLEStateAbsoluteModePadded ///< As above, but another byte of data has to be read as padding

class RasterImage;

 * Decoder for BMP-Files, as used by Windows and OS/2
class nsBMPDecoder : public Decoder


    // Specifies whether or not the BMP file will contain alpha data
    // If set to true and the BMP is 32BPP, the alpha data will be
    // retrieved from the 4th byte of image data per pixel 
    void SetUseAlphaData(PRBool useAlphaData);
    // Obtains the bits per pixel from the internal BIH header
    PRInt32 GetBitsPerPixel() const;
    // Obtains the width from the internal BIH header
    PRInt32 GetWidth() const;
    // Obtains the height from the internal BIH header
    PRInt32 GetHeight() const;
    // Obtains the internal output image buffer
    PRUint32* GetImageData();
    // Obtains the size of the compressed image resource
    PRInt32 GetCompressedImageSize() const;

    virtual void WriteInternal(const char* aBuffer, PRUint32 aCount);
    virtual void FinishInternal();


    /** Calculates the red-, green- and blueshift in mBitFields using
     * the bitmasks from mBitFields */
    NS_METHOD CalcBitShift();

    PRUint32 mPos;

    char mRawBuf[36];

    PRUint32 mLOH; ///< Length of the header

    PRUint32 mNumColors; ///< The number of used colors, i.e. the number of entries in mColors
    colorTable *mColors;

    bitFields mBitFields;

    PRUint32 *mImageData; ///< Pointer to the image data for the frame
    PRUint8 *mRow;      ///< Holds one raw line of the image
    PRUint32 mRowBytes; ///< How many bytes of the row were already received
    PRInt32 mCurLine;   ///< Index of the line of the image that's currently being decoded
    PRInt32 mOldLine;   ///< Previous index of the line 
    PRInt32 mCurPos;    ///< Index in the current line of the image

    ERLEState mState;   ///< Maintains the current state of the RLE decoding
    PRUint32 mStateData;///< Decoding information that is needed depending on mState

    /** Set mBFH from the raw data in mRawBuf, converting from little-endian
     * data to native data as necessary */
    void ProcessFileHeader();
    /** Set mBIH from the raw data in mRawBuf, converting from little-endian
     * data to native data as necessary */
    void ProcessInfoHeader();

    // Stores whether the image data stores alpha data, or if
    // the alpha data is unspecified and filled with a 
    // padding byte of 0.
    // When a 32BPP bitmap is stored in an ICO or CUR file, its 4th byte
    // is used for alpha transparency.  When it is stored in a BMP, its
    // 4th byte is reserved and is always 0.
    // Reference: 
    PRPackedBool mUseAlphaData;

/** Sets the pixel data in aDecoded to the given values.
 * @param aDecoded pointer to pixel to be set, will be incremented to point to the next pixel.
static inline void SetPixel(PRUint32*& aDecoded, PRUint8 aRed, PRUint8 aGreen, PRUint8 aBlue, PRUint8 aAlpha = 0xFF)
    *aDecoded++ = GFX_PACKED_PIXEL(aAlpha, aRed, aGreen, aBlue);

static inline void SetPixel(PRUint32*& aDecoded, PRUint8 idx, colorTable* aColors)
    SetPixel(aDecoded, aColors[idx].red, aColors[idx].green, aColors[idx].blue);

/** Sets two (or one if aCount = 1) pixels
 * @param aDecoded where the data is stored. Will be moved 4 resp 8 bytes
 * depending on whether one or two pixels are written.
 * @param aData The values for the two pixels
 * @param aCount Current count. Is decremented by one or two.
inline void Set4BitPixel(PRUint32*& aDecoded, PRUint8 aData,
                         PRUint32& aCount, colorTable* aColors)
    PRUint8 idx = aData >> 4;
    SetPixel(aDecoded, idx, aColors);
    if (--aCount > 0) {
        idx = aData & 0xF;
        SetPixel(aDecoded, idx, aColors);

} // namespace imagelib
} // namespace mozilla