/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef GFX_COLOR_H
#define GFX_COLOR_H
#include "mozilla/Attributes.h" // for MOZ_ALWAYS_INLINE
#include "mozilla/gfx/Types.h" // for mozilla::gfx::SurfaceFormatBit
/**
* Fast approximate division by 255. It has the property that
* for all 0 <= n <= 255*255, GFX_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 ((v)/255)
*/
#define GFX_DIVIDE_BY_255(v) \
(((((
unsigned)(v)) << 8) + ((
unsigned)(v)) + 255) >> 16)
/**
* Fast premultiply
*
* equivalent to (((c)*(a))/255)
*/
uint8_t MOZ_ALWAYS_INLINE gfxPreMultiply(uint8_t c, uint8_t a) {
return GFX_DIVIDE_BY_255((c) * (a));
}
/**
* Pack the 4 8-bit channels (A,R,G,B)
* into a 32-bit packed NON-premultiplied pixel.
*/
uint32_t MOZ_ALWAYS_INLINE gfxPackedPixelNoPreMultiply(uint8_t a, uint8_t r,
uint8_t g, uint8_t b) {
return (((a) << mozilla::gfx::SurfaceFormatBit::OS_A) |
((r) << mozilla::gfx::SurfaceFormatBit::OS_R) |
((g) << mozilla::gfx::SurfaceFormatBit::OS_G) |
((b) << mozilla::gfx::SurfaceFormatBit::OS_B));
}
/**
* Pack the 4 8-bit channels (A,R,G,B)
* into a 32-bit packed premultiplied pixel.
*/
uint32_t MOZ_ALWAYS_INLINE gfxPackedPixel(uint8_t a, uint8_t r, uint8_t g,
uint8_t b) {
if (a == 0x00)
return 0x00000000;
else if (a == 0xFF) {
return gfxPackedPixelNoPreMultiply(a, r, g, b);
}
else {
return ((a) << mozilla::gfx::SurfaceFormatBit::OS_A) |
(gfxPreMultiply(r, a) << mozilla::gfx::SurfaceFormatBit::OS_R) |
(gfxPreMultiply(g, a) << mozilla::gfx::SurfaceFormatBit::OS_G) |
(gfxPreMultiply(b, a) << mozilla::gfx::SurfaceFormatBit::OS_B);
}
}
#endif /* _GFX_COLOR_H */
