1 // Copyright 2013 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 // Utilities for processing transparent channel. 11 // 12 // Author: Skal (pascal.massimino (at) gmail.com) 13 14 #include <assert.h> 15 #include "./dsp.h" 16 17 // Tables can be faster on some platform but incur some extra binary size (~2k). 18 // #define USE_TABLES_FOR_ALPHA_MULT 19 20 // ----------------------------------------------------------------------------- 21 22 #define MFIX 24 // 24bit fixed-point arithmetic 23 #define HALF ((1u << MFIX) >> 1) 24 #define KINV_255 ((1u << MFIX) / 255u) 25 26 static uint32_t Mult(uint8_t x, uint32_t mult) { 27 const uint32_t v = (x * mult + HALF) >> MFIX; 28 assert(v <= 255); // <- 24bit precision is enough to ensure that. 29 return v; 30 } 31 32 #ifdef USE_TABLES_FOR_ALPHA_MULT 33 34 static const uint32_t kMultTables[2][256] = { 35 { // (255u << MFIX) / alpha 36 0x00000000, 0xff000000, 0x7f800000, 0x55000000, 0x3fc00000, 0x33000000, 37 0x2a800000, 0x246db6db, 0x1fe00000, 0x1c555555, 0x19800000, 0x172e8ba2, 38 0x15400000, 0x139d89d8, 0x1236db6d, 0x11000000, 0x0ff00000, 0x0f000000, 39 0x0e2aaaaa, 0x0d6bca1a, 0x0cc00000, 0x0c249249, 0x0b9745d1, 0x0b1642c8, 40 0x0aa00000, 0x0a333333, 0x09cec4ec, 0x0971c71c, 0x091b6db6, 0x08cb08d3, 41 0x08800000, 0x0839ce73, 0x07f80000, 0x07ba2e8b, 0x07800000, 0x07492492, 42 0x07155555, 0x06e45306, 0x06b5e50d, 0x0689d89d, 0x06600000, 0x063831f3, 43 0x06124924, 0x05ee23b8, 0x05cba2e8, 0x05aaaaaa, 0x058b2164, 0x056cefa8, 44 0x05500000, 0x05343eb1, 0x05199999, 0x05000000, 0x04e76276, 0x04cfb2b7, 45 0x04b8e38e, 0x04a2e8ba, 0x048db6db, 0x0479435e, 0x04658469, 0x045270d0, 46 0x04400000, 0x042e29f7, 0x041ce739, 0x040c30c3, 0x03fc0000, 0x03ec4ec4, 47 0x03dd1745, 0x03ce540f, 0x03c00000, 0x03b21642, 0x03a49249, 0x03976fc6, 48 0x038aaaaa, 0x037e3f1f, 0x03722983, 0x03666666, 0x035af286, 0x034fcace, 49 0x0344ec4e, 0x033a5440, 0x03300000, 0x0325ed09, 0x031c18f9, 0x0312818a, 50 0x03092492, 0x03000000, 0x02f711dc, 0x02ee5846, 0x02e5d174, 0x02dd7baf, 51 0x02d55555, 0x02cd5cd5, 0x02c590b2, 0x02bdef7b, 0x02b677d4, 0x02af286b, 52 0x02a80000, 0x02a0fd5c, 0x029a1f58, 0x029364d9, 0x028ccccc, 0x0286562d, 53 0x02800000, 0x0279c952, 0x0273b13b, 0x026db6db, 0x0267d95b, 0x026217ec, 54 0x025c71c7, 0x0256e62a, 0x0251745d, 0x024c1bac, 0x0246db6d, 0x0241b2f9, 55 0x023ca1af, 0x0237a6f4, 0x0232c234, 0x022df2df, 0x02293868, 0x02249249, 56 0x02200000, 0x021b810e, 0x021714fb, 0x0212bb51, 0x020e739c, 0x020a3d70, 57 0x02061861, 0x02020408, 0x01fe0000, 0x01fa0be8, 0x01f62762, 0x01f25213, 58 0x01ee8ba2, 0x01ead3ba, 0x01e72a07, 0x01e38e38, 0x01e00000, 0x01dc7f10, 59 0x01d90b21, 0x01d5a3e9, 0x01d24924, 0x01cefa8d, 0x01cbb7e3, 0x01c880e5, 60 0x01c55555, 0x01c234f7, 0x01bf1f8f, 0x01bc14e5, 0x01b914c1, 0x01b61eed, 61 0x01b33333, 0x01b05160, 0x01ad7943, 0x01aaaaaa, 0x01a7e567, 0x01a5294a, 62 0x01a27627, 0x019fcbd2, 0x019d2a20, 0x019a90e7, 0x01980000, 0x01957741, 63 0x0192f684, 0x01907da4, 0x018e0c7c, 0x018ba2e8, 0x018940c5, 0x0186e5f0, 64 0x01849249, 0x018245ae, 0x01800000, 0x017dc11f, 0x017b88ee, 0x0179574e, 65 0x01772c23, 0x01750750, 0x0172e8ba, 0x0170d045, 0x016ebdd7, 0x016cb157, 66 0x016aaaaa, 0x0168a9b9, 0x0166ae6a, 0x0164b8a7, 0x0162c859, 0x0160dd67, 67 0x015ef7bd, 0x015d1745, 0x015b3bea, 0x01596596, 0x01579435, 0x0155c7b4, 68 0x01540000, 0x01523d03, 0x01507eae, 0x014ec4ec, 0x014d0fac, 0x014b5edc, 69 0x0149b26c, 0x01480a4a, 0x01466666, 0x0144c6af, 0x01432b16, 0x0141938b, 70 0x01400000, 0x013e7063, 0x013ce4a9, 0x013b5cc0, 0x0139d89d, 0x01385830, 71 0x0136db6d, 0x01356246, 0x0133ecad, 0x01327a97, 0x01310bf6, 0x012fa0be, 72 0x012e38e3, 0x012cd459, 0x012b7315, 0x012a150a, 0x0128ba2e, 0x01276276, 73 0x01260dd6, 0x0124bc44, 0x01236db6, 0x01222222, 0x0120d97c, 0x011f93bc, 74 0x011e50d7, 0x011d10c4, 0x011bd37a, 0x011a98ef, 0x0119611a, 0x01182bf2, 75 0x0116f96f, 0x0115c988, 0x01149c34, 0x0113716a, 0x01124924, 0x01112358, 76 0x01100000, 0x010edf12, 0x010dc087, 0x010ca458, 0x010b8a7d, 0x010a72f0, 77 0x01095da8, 0x01084a9f, 0x010739ce, 0x01062b2e, 0x01051eb8, 0x01041465, 78 0x01030c30, 0x01020612, 0x01010204, 0x01000000 }, 79 { // alpha * KINV_255 80 0x00000000, 0x00010101, 0x00020202, 0x00030303, 0x00040404, 0x00050505, 81 0x00060606, 0x00070707, 0x00080808, 0x00090909, 0x000a0a0a, 0x000b0b0b, 82 0x000c0c0c, 0x000d0d0d, 0x000e0e0e, 0x000f0f0f, 0x00101010, 0x00111111, 83 0x00121212, 0x00131313, 0x00141414, 0x00151515, 0x00161616, 0x00171717, 84 0x00181818, 0x00191919, 0x001a1a1a, 0x001b1b1b, 0x001c1c1c, 0x001d1d1d, 85 0x001e1e1e, 0x001f1f1f, 0x00202020, 0x00212121, 0x00222222, 0x00232323, 86 0x00242424, 0x00252525, 0x00262626, 0x00272727, 0x00282828, 0x00292929, 87 0x002a2a2a, 0x002b2b2b, 0x002c2c2c, 0x002d2d2d, 0x002e2e2e, 0x002f2f2f, 88 0x00303030, 0x00313131, 0x00323232, 0x00333333, 0x00343434, 0x00353535, 89 0x00363636, 0x00373737, 0x00383838, 0x00393939, 0x003a3a3a, 0x003b3b3b, 90 0x003c3c3c, 0x003d3d3d, 0x003e3e3e, 0x003f3f3f, 0x00404040, 0x00414141, 91 0x00424242, 0x00434343, 0x00444444, 0x00454545, 0x00464646, 0x00474747, 92 0x00484848, 0x00494949, 0x004a4a4a, 0x004b4b4b, 0x004c4c4c, 0x004d4d4d, 93 0x004e4e4e, 0x004f4f4f, 0x00505050, 0x00515151, 0x00525252, 0x00535353, 94 0x00545454, 0x00555555, 0x00565656, 0x00575757, 0x00585858, 0x00595959, 95 0x005a5a5a, 0x005b5b5b, 0x005c5c5c, 0x005d5d5d, 0x005e5e5e, 0x005f5f5f, 96 0x00606060, 0x00616161, 0x00626262, 0x00636363, 0x00646464, 0x00656565, 97 0x00666666, 0x00676767, 0x00686868, 0x00696969, 0x006a6a6a, 0x006b6b6b, 98 0x006c6c6c, 0x006d6d6d, 0x006e6e6e, 0x006f6f6f, 0x00707070, 0x00717171, 99 0x00727272, 0x00737373, 0x00747474, 0x00757575, 0x00767676, 0x00777777, 100 0x00787878, 0x00797979, 0x007a7a7a, 0x007b7b7b, 0x007c7c7c, 0x007d7d7d, 101 0x007e7e7e, 0x007f7f7f, 0x00808080, 0x00818181, 0x00828282, 0x00838383, 102 0x00848484, 0x00858585, 0x00868686, 0x00878787, 0x00888888, 0x00898989, 103 0x008a8a8a, 0x008b8b8b, 0x008c8c8c, 0x008d8d8d, 0x008e8e8e, 0x008f8f8f, 104 0x00909090, 0x00919191, 0x00929292, 0x00939393, 0x00949494, 0x00959595, 105 0x00969696, 0x00979797, 0x00989898, 0x00999999, 0x009a9a9a, 0x009b9b9b, 106 0x009c9c9c, 0x009d9d9d, 0x009e9e9e, 0x009f9f9f, 0x00a0a0a0, 0x00a1a1a1, 107 0x00a2a2a2, 0x00a3a3a3, 0x00a4a4a4, 0x00a5a5a5, 0x00a6a6a6, 0x00a7a7a7, 108 0x00a8a8a8, 0x00a9a9a9, 0x00aaaaaa, 0x00ababab, 0x00acacac, 0x00adadad, 109 0x00aeaeae, 0x00afafaf, 0x00b0b0b0, 0x00b1b1b1, 0x00b2b2b2, 0x00b3b3b3, 110 0x00b4b4b4, 0x00b5b5b5, 0x00b6b6b6, 0x00b7b7b7, 0x00b8b8b8, 0x00b9b9b9, 111 0x00bababa, 0x00bbbbbb, 0x00bcbcbc, 0x00bdbdbd, 0x00bebebe, 0x00bfbfbf, 112 0x00c0c0c0, 0x00c1c1c1, 0x00c2c2c2, 0x00c3c3c3, 0x00c4c4c4, 0x00c5c5c5, 113 0x00c6c6c6, 0x00c7c7c7, 0x00c8c8c8, 0x00c9c9c9, 0x00cacaca, 0x00cbcbcb, 114 0x00cccccc, 0x00cdcdcd, 0x00cecece, 0x00cfcfcf, 0x00d0d0d0, 0x00d1d1d1, 115 0x00d2d2d2, 0x00d3d3d3, 0x00d4d4d4, 0x00d5d5d5, 0x00d6d6d6, 0x00d7d7d7, 116 0x00d8d8d8, 0x00d9d9d9, 0x00dadada, 0x00dbdbdb, 0x00dcdcdc, 0x00dddddd, 117 0x00dedede, 0x00dfdfdf, 0x00e0e0e0, 0x00e1e1e1, 0x00e2e2e2, 0x00e3e3e3, 118 0x00e4e4e4, 0x00e5e5e5, 0x00e6e6e6, 0x00e7e7e7, 0x00e8e8e8, 0x00e9e9e9, 119 0x00eaeaea, 0x00ebebeb, 0x00ececec, 0x00ededed, 0x00eeeeee, 0x00efefef, 120 0x00f0f0f0, 0x00f1f1f1, 0x00f2f2f2, 0x00f3f3f3, 0x00f4f4f4, 0x00f5f5f5, 121 0x00f6f6f6, 0x00f7f7f7, 0x00f8f8f8, 0x00f9f9f9, 0x00fafafa, 0x00fbfbfb, 122 0x00fcfcfc, 0x00fdfdfd, 0x00fefefe, 0x00ffffff } 123 }; 124 125 static WEBP_INLINE uint32_t GetScale(uint32_t a, int inverse) { 126 return kMultTables[!inverse][a]; 127 } 128 129 #else 130 131 static WEBP_INLINE uint32_t GetScale(uint32_t a, int inverse) { 132 return inverse ? (255u << MFIX) / a : a * KINV_255; 133 } 134 135 #endif // USE_TABLES_FOR_ALPHA_MULT 136 137 static void MultARGBRow(uint32_t* const ptr, int width, int inverse) { 138 int x; 139 for (x = 0; x < width; ++x) { 140 const uint32_t argb = ptr[x]; 141 if (argb < 0xff000000u) { // alpha < 255 142 if (argb <= 0x00ffffffu) { // alpha == 0 143 ptr[x] = 0; 144 } else { 145 const uint32_t alpha = (argb >> 24) & 0xff; 146 const uint32_t scale = GetScale(alpha, inverse); 147 uint32_t out = argb & 0xff000000u; 148 out |= Mult(argb >> 0, scale) << 0; 149 out |= Mult(argb >> 8, scale) << 8; 150 out |= Mult(argb >> 16, scale) << 16; 151 ptr[x] = out; 152 } 153 } 154 } 155 } 156 157 static void MultRow(uint8_t* const ptr, const uint8_t* const alpha, 158 int width, int inverse) { 159 int x; 160 for (x = 0; x < width; ++x) { 161 const uint32_t a = alpha[x]; 162 if (a != 255) { 163 if (a == 0) { 164 ptr[x] = 0; 165 } else { 166 const uint32_t scale = GetScale(a, inverse); 167 ptr[x] = Mult(ptr[x], scale); 168 } 169 } 170 } 171 } 172 173 #undef KINV_255 174 #undef HALF 175 #undef MFIX 176 177 void (*WebPMultARGBRow)(uint32_t* const ptr, int width, int inverse); 178 void (*WebPMultRow)(uint8_t* const ptr, const uint8_t* const alpha, 179 int width, int inverse); 180 181 //------------------------------------------------------------------------------ 182 // Generic per-plane calls 183 184 void WebPMultARGBRows(uint8_t* ptr, int stride, int width, int num_rows, 185 int inverse) { 186 int n; 187 for (n = 0; n < num_rows; ++n) { 188 WebPMultARGBRow((uint32_t*)ptr, width, inverse); 189 ptr += stride; 190 } 191 } 192 193 void WebPMultRows(uint8_t* ptr, int stride, 194 const uint8_t* alpha, int alpha_stride, 195 int width, int num_rows, int inverse) { 196 int n; 197 for (n = 0; n < num_rows; ++n) { 198 WebPMultRow(ptr, alpha, width, inverse); 199 ptr += stride; 200 alpha += alpha_stride; 201 } 202 } 203 204 //------------------------------------------------------------------------------ 205 // Premultiplied modes 206 207 // non dithered-modes 208 209 // (x * a * 32897) >> 23 is bit-wise equivalent to (int)(x * a / 255.) 210 // for all 8bit x or a. For bit-wise equivalence to (int)(x * a / 255. + .5), 211 // one can use instead: (x * a * 65793 + (1 << 23)) >> 24 212 #if 1 // (int)(x * a / 255.) 213 #define MULTIPLIER(a) ((a) * 32897U) 214 #define PREMULTIPLY(x, m) (((x) * (m)) >> 23) 215 #else // (int)(x * a / 255. + .5) 216 #define MULTIPLIER(a) ((a) * 65793U) 217 #define PREMULTIPLY(x, m) (((x) * (m) + (1U << 23)) >> 24) 218 #endif 219 220 static void ApplyAlphaMultiply(uint8_t* rgba, int alpha_first, 221 int w, int h, int stride) { 222 while (h-- > 0) { 223 uint8_t* const rgb = rgba + (alpha_first ? 1 : 0); 224 const uint8_t* const alpha = rgba + (alpha_first ? 0 : 3); 225 int i; 226 for (i = 0; i < w; ++i) { 227 const uint32_t a = alpha[4 * i]; 228 if (a != 0xff) { 229 const uint32_t mult = MULTIPLIER(a); 230 rgb[4 * i + 0] = PREMULTIPLY(rgb[4 * i + 0], mult); 231 rgb[4 * i + 1] = PREMULTIPLY(rgb[4 * i + 1], mult); 232 rgb[4 * i + 2] = PREMULTIPLY(rgb[4 * i + 2], mult); 233 } 234 } 235 rgba += stride; 236 } 237 } 238 #undef MULTIPLIER 239 #undef PREMULTIPLY 240 241 // rgbA4444 242 243 #define MULTIPLIER(a) ((a) * 0x1111) // 0x1111 ~= (1 << 16) / 15 244 245 static WEBP_INLINE uint8_t dither_hi(uint8_t x) { 246 return (x & 0xf0) | (x >> 4); 247 } 248 249 static WEBP_INLINE uint8_t dither_lo(uint8_t x) { 250 return (x & 0x0f) | (x << 4); 251 } 252 253 static WEBP_INLINE uint8_t multiply(uint8_t x, uint32_t m) { 254 return (x * m) >> 16; 255 } 256 257 static WEBP_INLINE void ApplyAlphaMultiply4444(uint8_t* rgba4444, 258 int w, int h, int stride, 259 int rg_byte_pos /* 0 or 1 */) { 260 while (h-- > 0) { 261 int i; 262 for (i = 0; i < w; ++i) { 263 const uint32_t rg = rgba4444[2 * i + rg_byte_pos]; 264 const uint32_t ba = rgba4444[2 * i + (rg_byte_pos ^ 1)]; 265 const uint8_t a = ba & 0x0f; 266 const uint32_t mult = MULTIPLIER(a); 267 const uint8_t r = multiply(dither_hi(rg), mult); 268 const uint8_t g = multiply(dither_lo(rg), mult); 269 const uint8_t b = multiply(dither_hi(ba), mult); 270 rgba4444[2 * i + rg_byte_pos] = (r & 0xf0) | ((g >> 4) & 0x0f); 271 rgba4444[2 * i + (rg_byte_pos ^ 1)] = (b & 0xf0) | a; 272 } 273 rgba4444 += stride; 274 } 275 } 276 #undef MULTIPLIER 277 278 static void ApplyAlphaMultiply_16b(uint8_t* rgba4444, 279 int w, int h, int stride) { 280 #ifdef WEBP_SWAP_16BIT_CSP 281 ApplyAlphaMultiply4444(rgba4444, w, h, stride, 1); 282 #else 283 ApplyAlphaMultiply4444(rgba4444, w, h, stride, 0); 284 #endif 285 } 286 287 void (*WebPApplyAlphaMultiply)(uint8_t*, int, int, int, int); 288 void (*WebPApplyAlphaMultiply4444)(uint8_t*, int, int, int); 289 290 //------------------------------------------------------------------------------ 291 // Init function 292 293 void WebPInitAlphaProcessing(void) { 294 WebPMultARGBRow = MultARGBRow; 295 WebPMultRow = MultRow; 296 WebPApplyAlphaMultiply = ApplyAlphaMultiply; 297 WebPApplyAlphaMultiply4444 = ApplyAlphaMultiply_16b; 298 } 299
