gfxColor.h (2152B)
1 /* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*- 2 * This Source Code Form is subject to the terms of the Mozilla Public 3 * License, v. 2.0. If a copy of the MPL was not distributed with this 4 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ 5 6 #ifndef GFX_COLOR_H 7 #define GFX_COLOR_H 8 9 #include "mozilla/Attributes.h" // for MOZ_ALWAYS_INLINE 10 #include "mozilla/gfx/Types.h" // for mozilla::gfx::SurfaceFormatBit 11 12 /** 13 * Fast approximate division by 255. It has the property that 14 * for all 0 <= n <= 255*255, GFX_DIVIDE_BY_255(n) == n/255. 15 * But it only uses two adds and two shifts instead of an 16 * integer division (which is expensive on many processors). 17 * 18 * equivalent to ((v)/255) 19 */ 20 #define GFX_DIVIDE_BY_255(v) \ 21 (((((unsigned)(v)) << 8) + ((unsigned)(v)) + 255) >> 16) 22 23 /** 24 * Fast premultiply 25 * 26 * equivalent to (((c)*(a))/255) 27 */ 28 uint8_t MOZ_ALWAYS_INLINE gfxPreMultiply(uint8_t c, uint8_t a) { 29 return GFX_DIVIDE_BY_255((c) * (a)); 30 } 31 32 /** 33 * Pack the 4 8-bit channels (A,R,G,B) 34 * into a 32-bit packed NON-premultiplied pixel. 35 */ 36 uint32_t MOZ_ALWAYS_INLINE gfxPackedPixelNoPreMultiply(uint8_t a, uint8_t r, 37 uint8_t g, uint8_t b) { 38 return (((a) << mozilla::gfx::SurfaceFormatBit::OS_A) | 39 ((r) << mozilla::gfx::SurfaceFormatBit::OS_R) | 40 ((g) << mozilla::gfx::SurfaceFormatBit::OS_G) | 41 ((b) << mozilla::gfx::SurfaceFormatBit::OS_B)); 42 } 43 44 /** 45 * Pack the 4 8-bit channels (A,R,G,B) 46 * into a 32-bit packed premultiplied pixel. 47 */ 48 uint32_t MOZ_ALWAYS_INLINE gfxPackedPixel(uint8_t a, uint8_t r, uint8_t g, 49 uint8_t b) { 50 if (a == 0x00) 51 return 0x00000000; 52 else if (a == 0xFF) { 53 return gfxPackedPixelNoPreMultiply(a, r, g, b); 54 } else { 55 return ((a) << mozilla::gfx::SurfaceFormatBit::OS_A) | 56 (gfxPreMultiply(r, a) << mozilla::gfx::SurfaceFormatBit::OS_R) | 57 (gfxPreMultiply(g, a) << mozilla::gfx::SurfaceFormatBit::OS_G) | 58 (gfxPreMultiply(b, a) << mozilla::gfx::SurfaceFormatBit::OS_B); 59 } 60 } 61 62 #endif /* _GFX_COLOR_H */