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move some RGB->YUV functions to yuv.h

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will be needed later

Change-Id: I6b9e460db2d398b9fecd5d3c1bbdb3f2f3d4f5db
This commit is contained in:
Pascal Massimino
2012-08-02 17:23:02 -07:00
parent 4b71ba035a
commit f94b04f045
2 changed files with 39 additions and 34 deletions
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33
src/dsp/yuv.h
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@ -5,7 +5,7 @@
// Additional IP Rights Grant: http://www.webmproject.org/license/additional/
// -----------------------------------------------------------------------------
//
// inline YUV->RGB conversion function
// inline YUV<->RGB conversion function
//
// Author: Skal (pascal.massimino@gmail.com)
@ -14,6 +14,9 @@
#include "../dec/decode_vp8.h"
//------------------------------------------------------------------------------
// YUV -> RGB conversion
#if defined(__cplusplus) || defined(c_plusplus)
extern "C" {
#endif
@ -95,6 +98,34 @@ static WEBP_INLINE uint32_t VP8Clip4Bits(uint8_t c) {
// Must be called before everything, to initialize the tables.
void VP8YUVInit(void);
//------------------------------------------------------------------------------
// RGB -> YUV conversion
// The exact naming is Y'CbCr, following the ITU-R BT.601 standard.
// More information at: http://en.wikipedia.org/wiki/YCbCr
// Y = 0.2569 * R + 0.5044 * G + 0.0979 * B + 16
// U = -0.1483 * R - 0.2911 * G + 0.4394 * B + 128
// V = 0.4394 * R - 0.3679 * G - 0.0715 * B + 128
// We use 16bit fixed point operations.
static WEBP_INLINE int VP8ClipUV(int v) {
v = (v + (257 << (YUV_FIX + 2 - 1))) >> (YUV_FIX + 2);
return ((v & ~0xff) == 0) ? v : (v < 0) ? 0 : 255;
}
static WEBP_INLINE int VP8RGBToY(int r, int g, int b) {
const int kRound = (1 << (YUV_FIX - 1)) + (16 << YUV_FIX);
const int luma = 16839 * r + 33059 * g + 6420 * b;
return (luma + kRound) >> YUV_FIX; // no need to clip
}
static WEBP_INLINE int VP8RGBToU(int r, int g, int b) {
return VP8ClipUV(-9719 * r - 19081 * g + 28800 * b);
}
static WEBP_INLINE int VP8RGBToV(int r, int g, int b) {
return VP8ClipUV(+28800 * r - 24116 * g - 4684 * b);
}
#if defined(__cplusplus) || defined(c_plusplus)
} // extern "C"
#endif