gfx/public/nsColor.h
author Timothy Nikkel <tnikkel@gmail.com>
Wed, 24 Jun 2009 21:17:24 +1200
changeset 29532 c97e700b3bbf04e70e63d925b667ae97a617c9eb
parent 28611 821405837446610ade88a2bdfc70b71677e58a05
permissions -rw-r--r--
Bug 494664. NS_ComposeColors needs to handle non-opaque background colors correctly. r=jrmuizel,sr=vlad.

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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#ifndef nsColor_h___
#define nsColor_h___

#include "gfxCore.h"
#include "nscore.h"

class nsAString;
class nsString;
class nsCString;

// A color is a 32 bit unsigned integer with four components: R, G, B
// and A.
typedef PRUint32 nscolor;

// Make a color out of r,g,b values. This assumes that the r,g,b values are
// properly constrained to 0-255. This also assumes that a is 255.
#define NS_RGB(_r,_g,_b) \
  ((nscolor) ((255 << 24) | ((_b)<<16) | ((_g)<<8) | (_r)))

// Make a color out of r,g,b,a values. This assumes that the r,g,b,a
// values are properly constrained to 0-255.
#define NS_RGBA(_r,_g,_b,_a) \
  ((nscolor) (((_a) << 24) | ((_b)<<16) | ((_g)<<8) | (_r)))

// Extract color components from nscolor
#define NS_GET_R(_rgba) ((PRUint8) ((_rgba) & 0xff))
#define NS_GET_G(_rgba) ((PRUint8) (((_rgba) >> 8) & 0xff))
#define NS_GET_B(_rgba) ((PRUint8) (((_rgba) >> 16) & 0xff))
#define NS_GET_A(_rgba) ((PRUint8) (((_rgba) >> 24) & 0xff))

// Fast approximate division by 255. It has the property that
// for all 0 <= n <= 255*255, FAST_DIVIDE_BY_255(n) == n/255.
// But it only uses two adds and two shifts instead of an 
// integer division (which is expensive on many processors).
//
// equivalent to target=v/255
#define FAST_DIVIDE_BY_255(target,v)               \
  PR_BEGIN_MACRO                                   \
    unsigned tmp_ = v;                             \
    target = ((tmp_ << 8) + tmp_ + 255) >> 16;     \
  PR_END_MACRO

// Translate a hex string to a color. Return true if it parses ok,
// otherwise return false.
// This accepts only 3 or 6 digits
NS_GFX_(PRBool) NS_HexToRGB(const nsString& aBuf, nscolor* aResult);

// Compose one NS_RGB color onto another. The result is what
// you get if you draw aFG on top of aBG with operator OVER.
NS_GFX_(nscolor) NS_ComposeColors(nscolor aBG, nscolor aFG);

// Translate a hex string to a color. Return true if it parses ok,
// otherwise return false.
// This version accepts 1 to 9 digits (missing digits are 0)
NS_GFX_(PRBool) NS_LooseHexToRGB(const nsString& aBuf, nscolor* aResult);

// There is no function to translate a color to a hex string, because
// the hex-string syntax does not support transparency.

// Translate a color name to a color. Return true if it parses ok,
// otherwise return false.
NS_GFX_(PRBool) NS_ColorNameToRGB(const nsAString& aBuf, nscolor* aResult);

// function to convert from HSL color space to RGB color space
// the float parameters are all expected to be in the range 0-1
NS_GFX_(nscolor) NS_HSL2RGB(float h, float s, float l);

#endif /* nsColor_h___ */