third_party/libwebp/dsp/yuv.h

   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@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_ */