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// Copyright 2010 Google Inc. All Rights Reserved.
//
// Use of this source code is governed by a BSD-style license
// that can be found in the COPYING file in the root of the source
// tree. An additional intellectual property rights grant can be found
// in the file PATENTS. All contributing project authors may
// be found in the AUTHORS file in the root of the source tree.
// -----------------------------------------------------------------------------
//
// inline YUV<->RGB conversion function
//
// 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 for RGB->YUV conversion (YUV_FIX).
//
// For the Y'CbCr to RGB conversion, the BT.601 specification reads:
// R = 1.164 * (Y-16) + 1.596 * (V-128)
// G = 1.164 * (Y-16) - 0.813 * (V-128) - 0.391 * (U-128)
// B = 1.164 * (Y-16) + 2.018 * (U-128)
// where Y is in the [16,235] range, and U/V in the [16,240] range.
//
// The fixed-point implementation used here is:
// R = (19077 . y + 26149 . v - 14234) >> 6
// G = (19077 . y - 6419 . u - 13320 . v + 8708) >> 6
// B = (19077 . y + 33050 . u - 17685) >> 6
// where the '.' operator is the mulhi_epu16 variant:
// a . b = ((a << 8) * b) >> 16
// that preserves 8 bits of fractional precision before final descaling.
// Author: Skal (pascal.massimino@gmail.com)
#ifndef WEBP_DSP_YUV_H_
#define WEBP_DSP_YUV_H_
#include "./dsp.h"
#include "../dec/decode_vp8.h"
#if defined(WEBP_EXPERIMENTAL_FEATURES)
// Do NOT activate this feature for real compression. This is only experimental!
// This flag is for comparison purpose against JPEG's "YUVj" natural colorspace.
// This colorspace is close to Rec.601's Y'CbCr model with the notable
// difference of allowing larger range for luma/chroma.
// See http://en.wikipedia.org/wiki/YCbCr#JPEG_conversion paragraph, and its
// difference with http://en.wikipedia.org/wiki/YCbCr#ITU-R_BT.601_conversion
// #define USE_YUVj
#endif
//------------------------------------------------------------------------------
// YUV -> RGB conversion
#ifdef __cplusplus
extern "C" {
#endif
enum {
YUV_FIX = 16, // fixed-point precision for RGB->YUV
YUV_HALF = 1 << (YUV_FIX - 1),
YUV_MASK = (256 << YUV_FIX) - 1,
YUV_RANGE_MIN = -227, // min value of r/g/b output
YUV_RANGE_MAX = 256 + 226, // max value of r/g/b output
YUV_FIX2 = 6, // fixed-point precision for YUV->RGB
YUV_HALF2 = 1 << YUV_FIX2 >> 1,
YUV_MASK2 = (256 << YUV_FIX2) - 1
};
//------------------------------------------------------------------------------
// slower on x86 by ~7-8%, but bit-exact with the SSE2/NEON version
static WEBP_INLINE int MultHi(int v, int coeff) { // _mm_mulhi_epu16 emulation
return (v * coeff) >> 8;
}
static WEBP_INLINE int VP8Clip8(int v) {
return ((v & ~YUV_MASK2) == 0) ? (v >> YUV_FIX2) : (v < 0) ? 0 : 255;
}
static WEBP_INLINE int VP8YUVToR(int y, int v) {
return VP8Clip8(MultHi(y, 19077) + MultHi(v, 26149) - 14234);
}
static WEBP_INLINE int VP8YUVToG(int y, int u, int v) {
return VP8Clip8(MultHi(y, 19077) - MultHi(u, 6419) - MultHi(v, 13320) + 8708);
}
static WEBP_INLINE int VP8YUVToB(int y, int u) {
return VP8Clip8(MultHi(y, 19077) + MultHi(u, 33050) - 17685);
}
static WEBP_INLINE void VP8YuvToRgb(int y, int u, int v,
uint8_t* const rgb) {
rgb[0] = VP8YUVToR(y, v);
rgb[1] = VP8YUVToG(y, u, v);
rgb[2] = VP8YUVToB(y, u);
}
static WEBP_INLINE void VP8YuvToBgr(int y, int u, int v,
uint8_t* const bgr) {
bgr[0] = VP8YUVToB(y, u);
bgr[1] = VP8YUVToG(y, u, v);
bgr[2] = VP8YUVToR(y, v);
}
static WEBP_INLINE void VP8YuvToRgb565(int y, int u, int v,
uint8_t* const rgb) {
const int r = VP8YUVToR(y, v); // 5 usable bits
const int g = VP8YUVToG(y, u, v); // 6 usable bits
const int b = VP8YUVToB(y, u); // 5 usable bits
const int rg = (r & 0xf8) | (g >> 5);
const int gb = ((g << 3) & 0xe0) | (b >> 3);
#ifdef WEBP_SWAP_16BIT_CSP
rgb[0] = gb;
rgb[1] = rg;
#else
rgb[0] = rg;
rgb[1] = gb;
#endif
}
static WEBP_INLINE void VP8YuvToRgba4444(int y, int u, int v,
uint8_t* const argb) {
const int r = VP8YUVToR(y, v); // 4 usable bits
const int g = VP8YUVToG(y, u, v); // 4 usable bits
const int b = VP8YUVToB(y, u); // 4 usable bits
const int rg = (r & 0xf0) | (g >> 4);
const int ba = (b & 0xf0) | 0x0f; // overwrite the lower 4 bits
#ifdef WEBP_SWAP_16BIT_CSP
argb[0] = ba;
argb[1] = rg;
#else
argb[0] = rg;
argb[1] = ba;
#endif
}
//-----------------------------------------------------------------------------
// Alpha handling variants
static WEBP_INLINE void VP8YuvToArgb(uint8_t y, uint8_t u, uint8_t v,
uint8_t* const argb) {
argb[0] = 0xff;
VP8YuvToRgb(y, u, v, argb + 1);
}
static WEBP_INLINE void VP8YuvToBgra(uint8_t y, uint8_t u, uint8_t v,
uint8_t* const bgra) {
VP8YuvToBgr(y, u, v, bgra);
bgra[3] = 0xff;
}
static WEBP_INLINE void VP8YuvToRgba(uint8_t y, uint8_t u, uint8_t v,
uint8_t* const rgba) {
VP8YuvToRgb(y, u, v, rgba);
rgba[3] = 0xff;
}
// Must be called before everything, to initialize the tables.
void VP8YUVInit(void);
//-----------------------------------------------------------------------------
// SSE2 extra functions (mostly for upsampling_sse2.c)
#if defined(WEBP_USE_SSE2)
// Process 32 pixels and store the result (16b, 24b or 32b per pixel) in *dst.
void VP8YuvToRgba32(const uint8_t* y, const uint8_t* u, const uint8_t* v,
uint8_t* dst);
void VP8YuvToRgb32(const uint8_t* y, const uint8_t* u, const uint8_t* v,
uint8_t* dst);
void VP8YuvToBgra32(const uint8_t* y, const uint8_t* u, const uint8_t* v,
uint8_t* dst);
void VP8YuvToBgr32(const uint8_t* y, const uint8_t* u, const uint8_t* v,
uint8_t* dst);
void VP8YuvToArgb32(const uint8_t* y, const uint8_t* u, const uint8_t* v,
uint8_t* dst);
void VP8YuvToRgba444432(const uint8_t* y, const uint8_t* u, const uint8_t* v,
uint8_t* dst);
void VP8YuvToRgb56532(const uint8_t* y, const uint8_t* u, const uint8_t* v,
uint8_t* dst);
#endif // WEBP_USE_SSE2
//------------------------------------------------------------------------------
// RGB -> YUV conversion
// Stub functions that can be called with various rounding values:
static WEBP_INLINE int VP8ClipUV(int uv, int rounding) {
uv = (uv + rounding + (128 << (YUV_FIX + 2))) >> (YUV_FIX + 2);
return ((uv & ~0xff) == 0) ? uv : (uv < 0) ? 0 : 255;
}
#ifndef USE_YUVj
static WEBP_INLINE int VP8RGBToY(int r, int g, int b, int rounding) {
const int luma = 16839 * r + 33059 * g + 6420 * b;
return (luma + rounding + (16 << YUV_FIX)) >> YUV_FIX; // no need to clip
}
static WEBP_INLINE int VP8RGBToU(int r, int g, int b, int rounding) {
const int u = -9719 * r - 19081 * g + 28800 * b;
return VP8ClipUV(u, rounding);
}
static WEBP_INLINE int VP8RGBToV(int r, int g, int b, int rounding) {
const int v = +28800 * r - 24116 * g - 4684 * b;
return VP8ClipUV(v, rounding);
}
#else
// This JPEG-YUV colorspace, only for comparison!
// These are also 16bit precision coefficients from Rec.601, but with full
// [0..255] output range.
static WEBP_INLINE int VP8RGBToY(int r, int g, int b, int rounding) {
const int luma = 19595 * r + 38470 * g + 7471 * b;
return (luma + rounding) >> YUV_FIX; // no need to clip
}
static WEBP_INLINE int VP8RGBToU(int r, int g, int b, int rounding) {
const int u = -11058 * r - 21710 * g + 32768 * b;
return VP8ClipUV(u, rounding);
}
static WEBP_INLINE int VP8RGBToV(int r, int g, int b, int rounding) {
const int v = 32768 * r - 27439 * g - 5329 * b;
return VP8ClipUV(v, rounding);
}
#endif // USE_YUVj
#ifdef __cplusplus
} // extern "C"
#endif
#endif /* WEBP_DSP_YUV_H_ */