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 // In the table-lookup version (WEBP_YUV_USE_TABLE), the common factor 25 // "1.164 * (Y-16)" can be handled as an offset in the VP8kClip[] table. 26 // So in this case the formulae should read: 27 // R = 1.164 * [Y + 1.371 * (V-128) ] - 18.624 28 // G = 1.164 * [Y - 0.698 * (V-128) - 0.336 * (U-128)] - 18.624 29 // B = 1.164 * [Y + 1.733 * (U-128)] - 18.624 30 // once factorized. 31 // For YUV->RGB conversion, only 14bit fixed precision is used (YUV_FIX2). 32 // That's the maximum possible for a convenient ARM implementation. 33 // 34 // Author: Skal (pascal.massimino (at) gmail.com) 35 36 #ifndef WEBP_DSP_YUV_H_ 37 #define WEBP_DSP_YUV_H_ 38 39 #include "./dsp.h" 40 #include "../dec/decode_vp8.h" 41 42 // Define the following to use the LUT-based code: 43 // #define WEBP_YUV_USE_TABLE 44 45 #if defined(WEBP_EXPERIMENTAL_FEATURES) 46 // Do NOT activate this feature for real compression. This is only experimental! 47 // This flag is for comparison purpose against JPEG's "YUVj" natural colorspace. 48 // This colorspace is close to Rec.601's Y'CbCr model with the notable 49 // difference of allowing larger range for luma/chroma. 50 // See http://en.wikipedia.org/wiki/YCbCr#JPEG_conversion paragraph, and its 51 // difference with http://en.wikipedia.org/wiki/YCbCr#ITU-R_BT.601_conversion 52 // #define USE_YUVj 53 #endif 54 55 //------------------------------------------------------------------------------ 56 // YUV -> RGB conversion 57 58 #ifdef __cplusplus 59 extern "C" { 60 #endif 61 62 enum { 63 YUV_FIX = 16, // fixed-point precision for RGB->YUV 64 YUV_HALF = 1 << (YUV_FIX - 1), 65 YUV_MASK = (256 << YUV_FIX) - 1, 66 YUV_RANGE_MIN = -227, // min value of r/g/b output 67 YUV_RANGE_MAX = 256 + 226, // max value of r/g/b output 68 69 YUV_FIX2 = 14, // fixed-point precision for YUV->RGB 70 YUV_HALF2 = 1 << (YUV_FIX2 - 1), 71 YUV_MASK2 = (256 << YUV_FIX2) - 1 72 }; 73 74 // These constants are 14b fixed-point version of ITU-R BT.601 constants. 75 #define kYScale 19077 // 1.164 = 255 / 219 76 #define kVToR 26149 // 1.596 = 255 / 112 * 0.701 77 #define kUToG 6419 // 0.391 = 255 / 112 * 0.886 * 0.114 / 0.587 78 #define kVToG 13320 // 0.813 = 255 / 112 * 0.701 * 0.299 / 0.587 79 #define kUToB 33050 // 2.018 = 255 / 112 * 0.886 80 #define kRCst (-kYScale * 16 - kVToR * 128 + YUV_HALF2) 81 #define kGCst (-kYScale * 16 + kUToG * 128 + kVToG * 128 + YUV_HALF2) 82 #define kBCst (-kYScale * 16 - kUToB * 128 + YUV_HALF2) 83 84 //------------------------------------------------------------------------------ 85 86 #if !defined(WEBP_YUV_USE_TABLE) 87 88 // slower on x86 by ~7-8%, but bit-exact with the SSE2 version 89 90 static WEBP_INLINE int VP8Clip8(int v) { 91 return ((v & ~YUV_MASK2) == 0) ? (v >> YUV_FIX2) : (v < 0) ? 0 : 255; 92 } 93 94 static WEBP_INLINE int VP8YUVToR(int y, int v) { 95 return VP8Clip8(kYScale * y + kVToR * v + kRCst); 96 } 97 98 static WEBP_INLINE int VP8YUVToG(int y, int u, int v) { 99 return VP8Clip8(kYScale * y - kUToG * u - kVToG * v + kGCst); 100 } 101 102 static WEBP_INLINE int VP8YUVToB(int y, int u) { 103 return VP8Clip8(kYScale * y + kUToB * u + kBCst); 104 } 105 106 static WEBP_INLINE void VP8YuvToRgb(int y, int u, int v, 107 uint8_t* const rgb) { 108 rgb[0] = VP8YUVToR(y, v); 109 rgb[1] = VP8YUVToG(y, u, v); 110 rgb[2] = VP8YUVToB(y, u); 111 } 112 113 static WEBP_INLINE void VP8YuvToBgr(int y, int u, int v, 114 uint8_t* const bgr) { 115 bgr[0] = VP8YUVToB(y, u); 116 bgr[1] = VP8YUVToG(y, u, v); 117 bgr[2] = VP8YUVToR(y, v); 118 } 119 120 static WEBP_INLINE void VP8YuvToRgb565(int y, int u, int v, 121 uint8_t* const rgb) { 122 const int r = VP8YUVToR(y, v); // 5 usable bits 123 const int g = VP8YUVToG(y, u, v); // 6 usable bits 124 const int b = VP8YUVToB(y, u); // 5 usable bits 125 const int rg = (r & 0xf8) | (g >> 5); 126 const int gb = ((g << 3) & 0xe0) | (b >> 3); 127 #ifdef WEBP_SWAP_16BIT_CSP 128 rgb[0] = gb; 129 rgb[1] = rg; 130 #else 131 rgb[0] = rg; 132 rgb[1] = gb; 133 #endif 134 } 135 136 static WEBP_INLINE void VP8YuvToRgba4444(int y, int u, int v, 137 uint8_t* const argb) { 138 const int r = VP8YUVToR(y, v); // 4 usable bits 139 const int g = VP8YUVToG(y, u, v); // 4 usable bits 140 const int b = VP8YUVToB(y, u); // 4 usable bits 141 const int rg = (r & 0xf0) | (g >> 4); 142 const int ba = (b & 0xf0) | 0x0f; // overwrite the lower 4 bits 143 #ifdef WEBP_SWAP_16BIT_CSP 144 argb[0] = ba; 145 argb[1] = rg; 146 #else 147 argb[0] = rg; 148 argb[1] = ba; 149 #endif 150 } 151 152 #else 153 154 // Table-based version, not totally equivalent to the SSE2 version. 155 // Rounding diff is only +/-1 though. 156 157 extern int16_t VP8kVToR[256], VP8kUToB[256]; 158 extern int32_t VP8kVToG[256], VP8kUToG[256]; 159 extern uint8_t VP8kClip[YUV_RANGE_MAX - YUV_RANGE_MIN]; 160 extern uint8_t VP8kClip4Bits[YUV_RANGE_MAX - YUV_RANGE_MIN]; 161 162 static WEBP_INLINE void VP8YuvToRgb(int y, int u, int v, 163 uint8_t* const rgb) { 164 const int r_off = VP8kVToR[v]; 165 const int g_off = (VP8kVToG[v] + VP8kUToG[u]) >> YUV_FIX; 166 const int b_off = VP8kUToB[u]; 167 rgb[0] = VP8kClip[y + r_off - YUV_RANGE_MIN]; 168 rgb[1] = VP8kClip[y + g_off - YUV_RANGE_MIN]; 169 rgb[2] = VP8kClip[y + b_off - YUV_RANGE_MIN]; 170 } 171 172 static WEBP_INLINE void VP8YuvToBgr(int y, int u, int v, 173 uint8_t* const bgr) { 174 const int r_off = VP8kVToR[v]; 175 const int g_off = (VP8kVToG[v] + VP8kUToG[u]) >> YUV_FIX; 176 const int b_off = VP8kUToB[u]; 177 bgr[0] = VP8kClip[y + b_off - YUV_RANGE_MIN]; 178 bgr[1] = VP8kClip[y + g_off - YUV_RANGE_MIN]; 179 bgr[2] = VP8kClip[y + r_off - YUV_RANGE_MIN]; 180 } 181 182 static WEBP_INLINE void VP8YuvToRgb565(int y, int u, int v, 183 uint8_t* const rgb) { 184 const int r_off = VP8kVToR[v]; 185 const int g_off = (VP8kVToG[v] + VP8kUToG[u]) >> YUV_FIX; 186 const int b_off = VP8kUToB[u]; 187 const int rg = ((VP8kClip[y + r_off - YUV_RANGE_MIN] & 0xf8) | 188 (VP8kClip[y + g_off - YUV_RANGE_MIN] >> 5)); 189 const int gb = (((VP8kClip[y + g_off - YUV_RANGE_MIN] << 3) & 0xe0) | 190 (VP8kClip[y + b_off - YUV_RANGE_MIN] >> 3)); 191 #ifdef WEBP_SWAP_16BIT_CSP 192 rgb[0] = gb; 193 rgb[1] = rg; 194 #else 195 rgb[0] = rg; 196 rgb[1] = gb; 197 #endif 198 } 199 200 static WEBP_INLINE void VP8YuvToRgba4444(int y, int u, int v, 201 uint8_t* const argb) { 202 const int r_off = VP8kVToR[v]; 203 const int g_off = (VP8kVToG[v] + VP8kUToG[u]) >> YUV_FIX; 204 const int b_off = VP8kUToB[u]; 205 const int rg = ((VP8kClip4Bits[y + r_off - YUV_RANGE_MIN] << 4) | 206 VP8kClip4Bits[y + g_off - YUV_RANGE_MIN]); 207 const int ba = (VP8kClip4Bits[y + b_off - YUV_RANGE_MIN] << 4) | 0x0f; 208 #ifdef WEBP_SWAP_16BIT_CSP 209 argb[0] = ba; 210 argb[1] = rg; 211 #else 212 argb[0] = rg; 213 argb[1] = ba; 214 #endif 215 } 216 217 #endif // WEBP_YUV_USE_TABLE 218 219 //----------------------------------------------------------------------------- 220 // Alpha handling variants 221 222 static WEBP_INLINE void VP8YuvToArgb(uint8_t y, uint8_t u, uint8_t v, 223 uint8_t* const argb) { 224 argb[0] = 0xff; 225 VP8YuvToRgb(y, u, v, argb + 1); 226 } 227 228 static WEBP_INLINE void VP8YuvToBgra(uint8_t y, uint8_t u, uint8_t v, 229 uint8_t* const bgra) { 230 VP8YuvToBgr(y, u, v, bgra); 231 bgra[3] = 0xff; 232 } 233 234 static WEBP_INLINE void VP8YuvToRgba(uint8_t y, uint8_t u, uint8_t v, 235 uint8_t* const rgba) { 236 VP8YuvToRgb(y, u, v, rgba); 237 rgba[3] = 0xff; 238 } 239 240 // Must be called before everything, to initialize the tables. 241 void VP8YUVInit(void); 242 243 //----------------------------------------------------------------------------- 244 // SSE2 extra functions (mostly for upsampling_sse2.c) 245 246 #if defined(WEBP_USE_SSE2) 247 248 // When the following is defined, tables are initialized statically, adding ~12k 249 // to the binary size. Otherwise, they are initialized at run-time (small cost). 250 #define WEBP_YUV_USE_SSE2_TABLES 251 252 #if defined(FANCY_UPSAMPLING) 253 // Process 32 pixels and store the result (24b or 32b per pixel) in *dst. 254 void VP8YuvToRgba32(const uint8_t* y, const uint8_t* u, const uint8_t* v, 255 uint8_t* dst); 256 void VP8YuvToRgb32(const uint8_t* y, const uint8_t* u, const uint8_t* v, 257 uint8_t* dst); 258 void VP8YuvToBgra32(const uint8_t* y, const uint8_t* u, const uint8_t* v, 259 uint8_t* dst); 260 void VP8YuvToBgr32(const uint8_t* y, const uint8_t* u, const uint8_t* v, 261 uint8_t* dst); 262 #endif // FANCY_UPSAMPLING 263 264 // Must be called to initialize tables before using the functions. 265 void VP8YUVInitSSE2(void); 266 267 #endif // WEBP_USE_SSE2 268 269 //------------------------------------------------------------------------------ 270 // RGB -> YUV conversion 271 272 // Stub functions that can be called with various rounding values: 273 static WEBP_INLINE int VP8ClipUV(int uv, int rounding) { 274 uv = (uv + rounding + (128 << (YUV_FIX + 2))) >> (YUV_FIX + 2); 275 return ((uv & ~0xff) == 0) ? uv : (uv < 0) ? 0 : 255; 276 } 277 278 #ifndef USE_YUVj 279 280 static WEBP_INLINE int VP8RGBToY(int r, int g, int b, int rounding) { 281 const int luma = 16839 * r + 33059 * g + 6420 * b; 282 return (luma + rounding + (16 << YUV_FIX)) >> YUV_FIX; // no need to clip 283 } 284 285 static WEBP_INLINE int VP8RGBToU(int r, int g, int b, int rounding) { 286 const int u = -9719 * r - 19081 * g + 28800 * b; 287 return VP8ClipUV(u, rounding); 288 } 289 290 static WEBP_INLINE int VP8RGBToV(int r, int g, int b, int rounding) { 291 const int v = +28800 * r - 24116 * g - 4684 * b; 292 return VP8ClipUV(v, rounding); 293 } 294 295 #else 296 297 // This JPEG-YUV colorspace, only for comparison! 298 // These are also 16bit precision coefficients from Rec.601, but with full 299 // [0..255] output range. 300 static WEBP_INLINE int VP8RGBToY(int r, int g, int b, int rounding) { 301 const int luma = 19595 * r + 38470 * g + 7471 * b; 302 return (luma + rounding) >> YUV_FIX; // no need to clip 303 } 304 305 static WEBP_INLINE int VP8RGBToU(int r, int g, int b, int rounding) { 306 const int u = -11058 * r - 21710 * g + 32768 * b; 307 return VP8ClipUV(u, rounding); 308 } 309 310 static WEBP_INLINE int VP8RGBToV(int r, int g, int b, int rounding) { 311 const int v = 32768 * r - 27439 * g - 5329 * b; 312 return VP8ClipUV(v, rounding); 313 } 314 315 #endif // USE_YUVj 316 317 #ifdef __cplusplus 318 } // extern "C" 319 #endif 320 321 #endif /* WEBP_DSP_YUV_H_ */ 322
