1 // Copyright 2010 Google Inc. All Rights Reserved. 2 // 3 // Use of this source code is governed by a BSD-style license 4 // that can be found in the COPYING file in the root of the source 5 // tree. An additional intellectual property rights grant can be found 6 // in the file PATENTS. All contributing project authors may 7 // be found in the AUTHORS file in the root of the source tree. 8 // ----------------------------------------------------------------------------- 9 // 10 // inline YUV<->RGB conversion function 11 // 12 // The exact naming is Y'CbCr, following the ITU-R BT.601 standard. 13 // More information at: http://en.wikipedia.org/wiki/YCbCr 14 // Y = 0.2569 * R + 0.5044 * G + 0.0979 * B + 16 15 // U = -0.1483 * R - 0.2911 * G + 0.4394 * B + 128 16 // V = 0.4394 * R - 0.3679 * G - 0.0715 * B + 128 17 // We use 16bit fixed point operations for RGB->YUV conversion (YUV_FIX). 18 // 19 // For the Y'CbCr to RGB conversion, the BT.601 specification reads: 20 // R = 1.164 * (Y-16) + 1.596 * (V-128) 21 // G = 1.164 * (Y-16) - 0.813 * (V-128) - 0.391 * (U-128) 22 // B = 1.164 * (Y-16) + 2.018 * (U-128) 23 // where Y is in the [16,235] range, and U/V in the [16,240] range. 24 // 25 // The fixed-point implementation used here is: 26 // R = (19077 . y + 26149 . v - 14234) >> 6 27 // G = (19077 . y - 6419 . u - 13320 . v + 8708) >> 6 28 // B = (19077 . y + 33050 . u - 17685) >> 6 29 // where the '.' operator is the mulhi_epu16 variant: 30 // a . b = ((a << 8) * b) >> 16 31 // that preserves 8 bits of fractional precision before final descaling. 32 33 // Author: Skal (pascal.massimino (at) gmail.com) 34 35 #ifndef WEBP_DSP_YUV_H_ 36 #define WEBP_DSP_YUV_H_ 37 38 #include "src/dsp/dsp.h" 39 #include "src/dec/vp8_dec.h" 40 41 //------------------------------------------------------------------------------ 42 // YUV -> RGB conversion 43 44 #ifdef __cplusplus 45 extern "C" { 46 #endif 47 48 enum { 49 YUV_FIX = 16, // fixed-point precision for RGB->YUV 50 YUV_HALF = 1 << (YUV_FIX - 1), 51 52 YUV_FIX2 = 6, // fixed-point precision for YUV->RGB 53 YUV_MASK2 = (256 << YUV_FIX2) - 1 54 }; 55 56 //------------------------------------------------------------------------------ 57 // slower on x86 by ~7-8%, but bit-exact with the SSE2/NEON version 58 59 static WEBP_INLINE int MultHi(int v, int coeff) { // _mm_mulhi_epu16 emulation 60 return (v * coeff) >> 8; 61 } 62 63 static WEBP_INLINE int VP8Clip8(int v) { 64 return ((v & ~YUV_MASK2) == 0) ? (v >> YUV_FIX2) : (v < 0) ? 0 : 255; 65 } 66 67 static WEBP_INLINE int VP8YUVToR(int y, int v) { 68 return VP8Clip8(MultHi(y, 19077) + MultHi(v, 26149) - 14234); 69 } 70 71 static WEBP_INLINE int VP8YUVToG(int y, int u, int v) { 72 return VP8Clip8(MultHi(y, 19077) - MultHi(u, 6419) - MultHi(v, 13320) + 8708); 73 } 74 75 static WEBP_INLINE int VP8YUVToB(int y, int u) { 76 return VP8Clip8(MultHi(y, 19077) + MultHi(u, 33050) - 17685); 77 } 78 79 static WEBP_INLINE void VP8YuvToRgb(int y, int u, int v, 80 uint8_t* const rgb) { 81 rgb[0] = VP8YUVToR(y, v); 82 rgb[1] = VP8YUVToG(y, u, v); 83 rgb[2] = VP8YUVToB(y, u); 84 } 85 86 static WEBP_INLINE void VP8YuvToBgr(int y, int u, int v, 87 uint8_t* const bgr) { 88 bgr[0] = VP8YUVToB(y, u); 89 bgr[1] = VP8YUVToG(y, u, v); 90 bgr[2] = VP8YUVToR(y, v); 91 } 92 93 static WEBP_INLINE void VP8YuvToRgb565(int y, int u, int v, 94 uint8_t* const rgb) { 95 const int r = VP8YUVToR(y, v); // 5 usable bits 96 const int g = VP8YUVToG(y, u, v); // 6 usable bits 97 const int b = VP8YUVToB(y, u); // 5 usable bits 98 const int rg = (r & 0xf8) | (g >> 5); 99 const int gb = ((g << 3) & 0xe0) | (b >> 3); 100 #if (WEBP_SWAP_16BIT_CSP == 1) 101 rgb[0] = gb; 102 rgb[1] = rg; 103 #else 104 rgb[0] = rg; 105 rgb[1] = gb; 106 #endif 107 } 108 109 static WEBP_INLINE void VP8YuvToRgba4444(int y, int u, int v, 110 uint8_t* const argb) { 111 const int r = VP8YUVToR(y, v); // 4 usable bits 112 const int g = VP8YUVToG(y, u, v); // 4 usable bits 113 const int b = VP8YUVToB(y, u); // 4 usable bits 114 const int rg = (r & 0xf0) | (g >> 4); 115 const int ba = (b & 0xf0) | 0x0f; // overwrite the lower 4 bits 116 #if (WEBP_SWAP_16BIT_CSP == 1) 117 argb[0] = ba; 118 argb[1] = rg; 119 #else 120 argb[0] = rg; 121 argb[1] = ba; 122 #endif 123 } 124 125 //----------------------------------------------------------------------------- 126 // Alpha handling variants 127 128 static WEBP_INLINE void VP8YuvToArgb(uint8_t y, uint8_t u, uint8_t v, 129 uint8_t* const argb) { 130 argb[0] = 0xff; 131 VP8YuvToRgb(y, u, v, argb + 1); 132 } 133 134 static WEBP_INLINE void VP8YuvToBgra(uint8_t y, uint8_t u, uint8_t v, 135 uint8_t* const bgra) { 136 VP8YuvToBgr(y, u, v, bgra); 137 bgra[3] = 0xff; 138 } 139 140 static WEBP_INLINE void VP8YuvToRgba(uint8_t y, uint8_t u, uint8_t v, 141 uint8_t* const rgba) { 142 VP8YuvToRgb(y, u, v, rgba); 143 rgba[3] = 0xff; 144 } 145 146 //----------------------------------------------------------------------------- 147 // SSE2 extra functions (mostly for upsampling_sse2.c) 148 149 #if defined(WEBP_USE_SSE2) 150 151 // Process 32 pixels and store the result (16b, 24b or 32b per pixel) in *dst. 152 void VP8YuvToRgba32_SSE2(const uint8_t* y, const uint8_t* u, const uint8_t* v, 153 uint8_t* dst); 154 void VP8YuvToRgb32_SSE2(const uint8_t* y, const uint8_t* u, const uint8_t* v, 155 uint8_t* dst); 156 void VP8YuvToBgra32_SSE2(const uint8_t* y, const uint8_t* u, const uint8_t* v, 157 uint8_t* dst); 158 void VP8YuvToBgr32_SSE2(const uint8_t* y, const uint8_t* u, const uint8_t* v, 159 uint8_t* dst); 160 void VP8YuvToArgb32_SSE2(const uint8_t* y, const uint8_t* u, const uint8_t* v, 161 uint8_t* dst); 162 void VP8YuvToRgba444432_SSE2(const uint8_t* y, const uint8_t* u, 163 const uint8_t* v, uint8_t* dst); 164 void VP8YuvToRgb56532_SSE2(const uint8_t* y, const uint8_t* u, const uint8_t* v, 165 uint8_t* dst); 166 167 #endif // WEBP_USE_SSE2 168 169 //------------------------------------------------------------------------------ 170 // RGB -> YUV conversion 171 172 // Stub functions that can be called with various rounding values: 173 static WEBP_INLINE int VP8ClipUV(int uv, int rounding) { 174 uv = (uv + rounding + (128 << (YUV_FIX + 2))) >> (YUV_FIX + 2); 175 return ((uv & ~0xff) == 0) ? uv : (uv < 0) ? 0 : 255; 176 } 177 178 static WEBP_INLINE int VP8RGBToY(int r, int g, int b, int rounding) { 179 const int luma = 16839 * r + 33059 * g + 6420 * b; 180 return (luma + rounding + (16 << YUV_FIX)) >> YUV_FIX; // no need to clip 181 } 182 183 static WEBP_INLINE int VP8RGBToU(int r, int g, int b, int rounding) { 184 const int u = -9719 * r - 19081 * g + 28800 * b; 185 return VP8ClipUV(u, rounding); 186 } 187 188 static WEBP_INLINE int VP8RGBToV(int r, int g, int b, int rounding) { 189 const int v = +28800 * r - 24116 * g - 4684 * b; 190 return VP8ClipUV(v, rounding); 191 } 192 193 #ifdef __cplusplus 194 } // extern "C" 195 #endif 196 197 #endif /* WEBP_DSP_YUV_H_ */ 198
