alpha_processing.c 15.6 KB
Newer Older
wester committed
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397
// Copyright 2013 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.
// -----------------------------------------------------------------------------
//
// Utilities for processing transparent channel.
//
// Author: Skal (pascal.massimino@gmail.com)

#include <assert.h>
#include "./dsp.h"

// Tables can be faster on some platform but incur some extra binary size (~2k).
// #define USE_TABLES_FOR_ALPHA_MULT

// -----------------------------------------------------------------------------

#define MFIX 24    // 24bit fixed-point arithmetic
#define HALF ((1u << MFIX) >> 1)
#define KINV_255 ((1u << MFIX) / 255u)

static uint32_t Mult(uint8_t x, uint32_t mult) {
  const uint32_t v = (x * mult + HALF) >> MFIX;
  assert(v <= 255);  // <- 24bit precision is enough to ensure that.
  return v;
}

#ifdef USE_TABLES_FOR_ALPHA_MULT

static const uint32_t kMultTables[2][256] = {
  {    // (255u << MFIX) / alpha
    0x00000000, 0xff000000, 0x7f800000, 0x55000000, 0x3fc00000, 0x33000000,
    0x2a800000, 0x246db6db, 0x1fe00000, 0x1c555555, 0x19800000, 0x172e8ba2,
    0x15400000, 0x139d89d8, 0x1236db6d, 0x11000000, 0x0ff00000, 0x0f000000,
    0x0e2aaaaa, 0x0d6bca1a, 0x0cc00000, 0x0c249249, 0x0b9745d1, 0x0b1642c8,
    0x0aa00000, 0x0a333333, 0x09cec4ec, 0x0971c71c, 0x091b6db6, 0x08cb08d3,
    0x08800000, 0x0839ce73, 0x07f80000, 0x07ba2e8b, 0x07800000, 0x07492492,
    0x07155555, 0x06e45306, 0x06b5e50d, 0x0689d89d, 0x06600000, 0x063831f3,
    0x06124924, 0x05ee23b8, 0x05cba2e8, 0x05aaaaaa, 0x058b2164, 0x056cefa8,
    0x05500000, 0x05343eb1, 0x05199999, 0x05000000, 0x04e76276, 0x04cfb2b7,
    0x04b8e38e, 0x04a2e8ba, 0x048db6db, 0x0479435e, 0x04658469, 0x045270d0,
    0x04400000, 0x042e29f7, 0x041ce739, 0x040c30c3, 0x03fc0000, 0x03ec4ec4,
    0x03dd1745, 0x03ce540f, 0x03c00000, 0x03b21642, 0x03a49249, 0x03976fc6,
    0x038aaaaa, 0x037e3f1f, 0x03722983, 0x03666666, 0x035af286, 0x034fcace,
    0x0344ec4e, 0x033a5440, 0x03300000, 0x0325ed09, 0x031c18f9, 0x0312818a,
    0x03092492, 0x03000000, 0x02f711dc, 0x02ee5846, 0x02e5d174, 0x02dd7baf,
    0x02d55555, 0x02cd5cd5, 0x02c590b2, 0x02bdef7b, 0x02b677d4, 0x02af286b,
    0x02a80000, 0x02a0fd5c, 0x029a1f58, 0x029364d9, 0x028ccccc, 0x0286562d,
    0x02800000, 0x0279c952, 0x0273b13b, 0x026db6db, 0x0267d95b, 0x026217ec,
    0x025c71c7, 0x0256e62a, 0x0251745d, 0x024c1bac, 0x0246db6d, 0x0241b2f9,
    0x023ca1af, 0x0237a6f4, 0x0232c234, 0x022df2df, 0x02293868, 0x02249249,
    0x02200000, 0x021b810e, 0x021714fb, 0x0212bb51, 0x020e739c, 0x020a3d70,
    0x02061861, 0x02020408, 0x01fe0000, 0x01fa0be8, 0x01f62762, 0x01f25213,
    0x01ee8ba2, 0x01ead3ba, 0x01e72a07, 0x01e38e38, 0x01e00000, 0x01dc7f10,
    0x01d90b21, 0x01d5a3e9, 0x01d24924, 0x01cefa8d, 0x01cbb7e3, 0x01c880e5,
    0x01c55555, 0x01c234f7, 0x01bf1f8f, 0x01bc14e5, 0x01b914c1, 0x01b61eed,
    0x01b33333, 0x01b05160, 0x01ad7943, 0x01aaaaaa, 0x01a7e567, 0x01a5294a,
    0x01a27627, 0x019fcbd2, 0x019d2a20, 0x019a90e7, 0x01980000, 0x01957741,
    0x0192f684, 0x01907da4, 0x018e0c7c, 0x018ba2e8, 0x018940c5, 0x0186e5f0,
    0x01849249, 0x018245ae, 0x01800000, 0x017dc11f, 0x017b88ee, 0x0179574e,
    0x01772c23, 0x01750750, 0x0172e8ba, 0x0170d045, 0x016ebdd7, 0x016cb157,
    0x016aaaaa, 0x0168a9b9, 0x0166ae6a, 0x0164b8a7, 0x0162c859, 0x0160dd67,
    0x015ef7bd, 0x015d1745, 0x015b3bea, 0x01596596, 0x01579435, 0x0155c7b4,
    0x01540000, 0x01523d03, 0x01507eae, 0x014ec4ec, 0x014d0fac, 0x014b5edc,
    0x0149b26c, 0x01480a4a, 0x01466666, 0x0144c6af, 0x01432b16, 0x0141938b,
    0x01400000, 0x013e7063, 0x013ce4a9, 0x013b5cc0, 0x0139d89d, 0x01385830,
    0x0136db6d, 0x01356246, 0x0133ecad, 0x01327a97, 0x01310bf6, 0x012fa0be,
    0x012e38e3, 0x012cd459, 0x012b7315, 0x012a150a, 0x0128ba2e, 0x01276276,
    0x01260dd6, 0x0124bc44, 0x01236db6, 0x01222222, 0x0120d97c, 0x011f93bc,
    0x011e50d7, 0x011d10c4, 0x011bd37a, 0x011a98ef, 0x0119611a, 0x01182bf2,
    0x0116f96f, 0x0115c988, 0x01149c34, 0x0113716a, 0x01124924, 0x01112358,
    0x01100000, 0x010edf12, 0x010dc087, 0x010ca458, 0x010b8a7d, 0x010a72f0,
    0x01095da8, 0x01084a9f, 0x010739ce, 0x01062b2e, 0x01051eb8, 0x01041465,
    0x01030c30, 0x01020612, 0x01010204, 0x01000000 },
  {   // alpha * KINV_255
    0x00000000, 0x00010101, 0x00020202, 0x00030303, 0x00040404, 0x00050505,
    0x00060606, 0x00070707, 0x00080808, 0x00090909, 0x000a0a0a, 0x000b0b0b,
    0x000c0c0c, 0x000d0d0d, 0x000e0e0e, 0x000f0f0f, 0x00101010, 0x00111111,
    0x00121212, 0x00131313, 0x00141414, 0x00151515, 0x00161616, 0x00171717,
    0x00181818, 0x00191919, 0x001a1a1a, 0x001b1b1b, 0x001c1c1c, 0x001d1d1d,
    0x001e1e1e, 0x001f1f1f, 0x00202020, 0x00212121, 0x00222222, 0x00232323,
    0x00242424, 0x00252525, 0x00262626, 0x00272727, 0x00282828, 0x00292929,
    0x002a2a2a, 0x002b2b2b, 0x002c2c2c, 0x002d2d2d, 0x002e2e2e, 0x002f2f2f,
    0x00303030, 0x00313131, 0x00323232, 0x00333333, 0x00343434, 0x00353535,
    0x00363636, 0x00373737, 0x00383838, 0x00393939, 0x003a3a3a, 0x003b3b3b,
    0x003c3c3c, 0x003d3d3d, 0x003e3e3e, 0x003f3f3f, 0x00404040, 0x00414141,
    0x00424242, 0x00434343, 0x00444444, 0x00454545, 0x00464646, 0x00474747,
    0x00484848, 0x00494949, 0x004a4a4a, 0x004b4b4b, 0x004c4c4c, 0x004d4d4d,
    0x004e4e4e, 0x004f4f4f, 0x00505050, 0x00515151, 0x00525252, 0x00535353,
    0x00545454, 0x00555555, 0x00565656, 0x00575757, 0x00585858, 0x00595959,
    0x005a5a5a, 0x005b5b5b, 0x005c5c5c, 0x005d5d5d, 0x005e5e5e, 0x005f5f5f,
    0x00606060, 0x00616161, 0x00626262, 0x00636363, 0x00646464, 0x00656565,
    0x00666666, 0x00676767, 0x00686868, 0x00696969, 0x006a6a6a, 0x006b6b6b,
    0x006c6c6c, 0x006d6d6d, 0x006e6e6e, 0x006f6f6f, 0x00707070, 0x00717171,
    0x00727272, 0x00737373, 0x00747474, 0x00757575, 0x00767676, 0x00777777,
    0x00787878, 0x00797979, 0x007a7a7a, 0x007b7b7b, 0x007c7c7c, 0x007d7d7d,
    0x007e7e7e, 0x007f7f7f, 0x00808080, 0x00818181, 0x00828282, 0x00838383,
    0x00848484, 0x00858585, 0x00868686, 0x00878787, 0x00888888, 0x00898989,
    0x008a8a8a, 0x008b8b8b, 0x008c8c8c, 0x008d8d8d, 0x008e8e8e, 0x008f8f8f,
    0x00909090, 0x00919191, 0x00929292, 0x00939393, 0x00949494, 0x00959595,
    0x00969696, 0x00979797, 0x00989898, 0x00999999, 0x009a9a9a, 0x009b9b9b,
    0x009c9c9c, 0x009d9d9d, 0x009e9e9e, 0x009f9f9f, 0x00a0a0a0, 0x00a1a1a1,
    0x00a2a2a2, 0x00a3a3a3, 0x00a4a4a4, 0x00a5a5a5, 0x00a6a6a6, 0x00a7a7a7,
    0x00a8a8a8, 0x00a9a9a9, 0x00aaaaaa, 0x00ababab, 0x00acacac, 0x00adadad,
    0x00aeaeae, 0x00afafaf, 0x00b0b0b0, 0x00b1b1b1, 0x00b2b2b2, 0x00b3b3b3,
    0x00b4b4b4, 0x00b5b5b5, 0x00b6b6b6, 0x00b7b7b7, 0x00b8b8b8, 0x00b9b9b9,
    0x00bababa, 0x00bbbbbb, 0x00bcbcbc, 0x00bdbdbd, 0x00bebebe, 0x00bfbfbf,
    0x00c0c0c0, 0x00c1c1c1, 0x00c2c2c2, 0x00c3c3c3, 0x00c4c4c4, 0x00c5c5c5,
    0x00c6c6c6, 0x00c7c7c7, 0x00c8c8c8, 0x00c9c9c9, 0x00cacaca, 0x00cbcbcb,
    0x00cccccc, 0x00cdcdcd, 0x00cecece, 0x00cfcfcf, 0x00d0d0d0, 0x00d1d1d1,
    0x00d2d2d2, 0x00d3d3d3, 0x00d4d4d4, 0x00d5d5d5, 0x00d6d6d6, 0x00d7d7d7,
    0x00d8d8d8, 0x00d9d9d9, 0x00dadada, 0x00dbdbdb, 0x00dcdcdc, 0x00dddddd,
    0x00dedede, 0x00dfdfdf, 0x00e0e0e0, 0x00e1e1e1, 0x00e2e2e2, 0x00e3e3e3,
    0x00e4e4e4, 0x00e5e5e5, 0x00e6e6e6, 0x00e7e7e7, 0x00e8e8e8, 0x00e9e9e9,
    0x00eaeaea, 0x00ebebeb, 0x00ececec, 0x00ededed, 0x00eeeeee, 0x00efefef,
    0x00f0f0f0, 0x00f1f1f1, 0x00f2f2f2, 0x00f3f3f3, 0x00f4f4f4, 0x00f5f5f5,
    0x00f6f6f6, 0x00f7f7f7, 0x00f8f8f8, 0x00f9f9f9, 0x00fafafa, 0x00fbfbfb,
    0x00fcfcfc, 0x00fdfdfd, 0x00fefefe, 0x00ffffff }
};

static WEBP_INLINE uint32_t GetScale(uint32_t a, int inverse) {
  return kMultTables[!inverse][a];
}

#else

static WEBP_INLINE uint32_t GetScale(uint32_t a, int inverse) {
  return inverse ? (255u << MFIX) / a : a * KINV_255;
}

#endif    // USE_TABLES_FOR_ALPHA_MULT

void WebPMultARGBRowC(uint32_t* const ptr, int width, int inverse) {
  int x;
  for (x = 0; x < width; ++x) {
    const uint32_t argb = ptr[x];
    if (argb < 0xff000000u) {      // alpha < 255
      if (argb <= 0x00ffffffu) {   // alpha == 0
        ptr[x] = 0;
      } else {
        const uint32_t alpha = (argb >> 24) & 0xff;
        const uint32_t scale = GetScale(alpha, inverse);
        uint32_t out = argb & 0xff000000u;
        out |= Mult(argb >>  0, scale) <<  0;
        out |= Mult(argb >>  8, scale) <<  8;
        out |= Mult(argb >> 16, scale) << 16;
        ptr[x] = out;
      }
    }
  }
}

void WebPMultRowC(uint8_t* const ptr, const uint8_t* const alpha,
                  int width, int inverse) {
  int x;
  for (x = 0; x < width; ++x) {
    const uint32_t a = alpha[x];
    if (a != 255) {
      if (a == 0) {
        ptr[x] = 0;
      } else {
        const uint32_t scale = GetScale(a, inverse);
        ptr[x] = Mult(ptr[x], scale);
      }
    }
  }
}

#undef KINV_255
#undef HALF
#undef MFIX

void (*WebPMultARGBRow)(uint32_t* const ptr, int width, int inverse);
void (*WebPMultRow)(uint8_t* const ptr, const uint8_t* const alpha,
                    int width, int inverse);

//------------------------------------------------------------------------------
// Generic per-plane calls

void WebPMultARGBRows(uint8_t* ptr, int stride, int width, int num_rows,
                      int inverse) {
  int n;
  for (n = 0; n < num_rows; ++n) {
    WebPMultARGBRow((uint32_t*)ptr, width, inverse);
    ptr += stride;
  }
}

void WebPMultRows(uint8_t* ptr, int stride,
                  const uint8_t* alpha, int alpha_stride,
                  int width, int num_rows, int inverse) {
  int n;
  for (n = 0; n < num_rows; ++n) {
    WebPMultRow(ptr, alpha, width, inverse);
    ptr += stride;
    alpha += alpha_stride;
  }
}

//------------------------------------------------------------------------------
// Premultiplied modes

// non dithered-modes

// (x * a * 32897) >> 23 is bit-wise equivalent to (int)(x * a / 255.)
// for all 8bit x or a. For bit-wise equivalence to (int)(x * a / 255. + .5),
// one can use instead: (x * a * 65793 + (1 << 23)) >> 24
#if 1     // (int)(x * a / 255.)
#define MULTIPLIER(a)   ((a) * 32897U)
#define PREMULTIPLY(x, m) (((x) * (m)) >> 23)
#else     // (int)(x * a / 255. + .5)
#define MULTIPLIER(a) ((a) * 65793U)
#define PREMULTIPLY(x, m) (((x) * (m) + (1U << 23)) >> 24)
#endif

static void ApplyAlphaMultiply(uint8_t* rgba, int alpha_first,
                               int w, int h, int stride) {
  while (h-- > 0) {
    uint8_t* const rgb = rgba + (alpha_first ? 1 : 0);
    const uint8_t* const alpha = rgba + (alpha_first ? 0 : 3);
    int i;
    for (i = 0; i < w; ++i) {
      const uint32_t a = alpha[4 * i];
      if (a != 0xff) {
        const uint32_t mult = MULTIPLIER(a);
        rgb[4 * i + 0] = PREMULTIPLY(rgb[4 * i + 0], mult);
        rgb[4 * i + 1] = PREMULTIPLY(rgb[4 * i + 1], mult);
        rgb[4 * i + 2] = PREMULTIPLY(rgb[4 * i + 2], mult);
      }
    }
    rgba += stride;
  }
}
#undef MULTIPLIER
#undef PREMULTIPLY

// rgbA4444

#define MULTIPLIER(a)  ((a) * 0x1111)    // 0x1111 ~= (1 << 16) / 15

static WEBP_INLINE uint8_t dither_hi(uint8_t x) {
  return (x & 0xf0) | (x >> 4);
}

static WEBP_INLINE uint8_t dither_lo(uint8_t x) {
  return (x & 0x0f) | (x << 4);
}

static WEBP_INLINE uint8_t multiply(uint8_t x, uint32_t m) {
  return (x * m) >> 16;
}

static WEBP_INLINE void ApplyAlphaMultiply4444(uint8_t* rgba4444,
                                               int w, int h, int stride,
                                               int rg_byte_pos /* 0 or 1 */) {
  while (h-- > 0) {
    int i;
    for (i = 0; i < w; ++i) {
      const uint32_t rg = rgba4444[2 * i + rg_byte_pos];
      const uint32_t ba = rgba4444[2 * i + (rg_byte_pos ^ 1)];
      const uint8_t a = ba & 0x0f;
      const uint32_t mult = MULTIPLIER(a);
      const uint8_t r = multiply(dither_hi(rg), mult);
      const uint8_t g = multiply(dither_lo(rg), mult);
      const uint8_t b = multiply(dither_hi(ba), mult);
      rgba4444[2 * i + rg_byte_pos] = (r & 0xf0) | ((g >> 4) & 0x0f);
      rgba4444[2 * i + (rg_byte_pos ^ 1)] = (b & 0xf0) | a;
    }
    rgba4444 += stride;
  }
}
#undef MULTIPLIER

static void ApplyAlphaMultiply_16b(uint8_t* rgba4444,
                                   int w, int h, int stride) {
#ifdef WEBP_SWAP_16BIT_CSP
  ApplyAlphaMultiply4444(rgba4444, w, h, stride, 1);
#else
  ApplyAlphaMultiply4444(rgba4444, w, h, stride, 0);
#endif
}

static int DispatchAlpha_C(const uint8_t* alpha, int alpha_stride,
                           int width, int height,
                           uint8_t* dst, int dst_stride) {
  uint32_t alpha_mask = 0xff;
  int i, j;

  for (j = 0; j < height; ++j) {
    for (i = 0; i < width; ++i) {
      const uint32_t alpha_value = alpha[i];
      dst[4 * i] = alpha_value;
      alpha_mask &= alpha_value;
    }
    alpha += alpha_stride;
    dst += dst_stride;
  }

  return (alpha_mask != 0xff);
}

static void DispatchAlphaToGreen_C(const uint8_t* alpha, int alpha_stride,
                                   int width, int height,
                                   uint32_t* dst, int dst_stride) {
  int i, j;
  for (j = 0; j < height; ++j) {
    for (i = 0; i < width; ++i) {
      dst[i] = alpha[i] << 8;  // leave A/R/B channels zero'd.
    }
    alpha += alpha_stride;
    dst += dst_stride;
  }
}

static int ExtractAlpha_C(const uint8_t* argb, int argb_stride,
                          int width, int height,
                          uint8_t* alpha, int alpha_stride) {
  uint8_t alpha_mask = 0xff;
  int i, j;

  for (j = 0; j < height; ++j) {
    for (i = 0; i < width; ++i) {
      const uint8_t alpha_value = argb[4 * i];
      alpha[i] = alpha_value;
      alpha_mask &= alpha_value;
    }
    argb += argb_stride;
    alpha += alpha_stride;
  }
  return (alpha_mask == 0xff);
}

static void ExtractGreen_C(const uint32_t* argb, uint8_t* alpha, int size) {
  int i;
  for (i = 0; i < size; ++i) alpha[i] = argb[i] >> 8;
}

void (*WebPApplyAlphaMultiply)(uint8_t*, int, int, int, int);
void (*WebPApplyAlphaMultiply4444)(uint8_t*, int, int, int);
int (*WebPDispatchAlpha)(const uint8_t*, int, int, int, uint8_t*, int);
void (*WebPDispatchAlphaToGreen)(const uint8_t*, int, int, int, uint32_t*, int);
int (*WebPExtractAlpha)(const uint8_t*, int, int, int, uint8_t*, int);
void (*WebPExtractGreen)(const uint32_t* argb, uint8_t* alpha, int size);

//------------------------------------------------------------------------------
// Init function

extern void WebPInitAlphaProcessingMIPSdspR2(void);
extern void WebPInitAlphaProcessingSSE2(void);
extern void WebPInitAlphaProcessingSSE41(void);
extern void WebPInitAlphaProcessingNEON(void);

static volatile VP8CPUInfo alpha_processing_last_cpuinfo_used =
    (VP8CPUInfo)&alpha_processing_last_cpuinfo_used;

WEBP_TSAN_IGNORE_FUNCTION void WebPInitAlphaProcessing(void) {
  if (alpha_processing_last_cpuinfo_used == VP8GetCPUInfo) return;

  WebPMultARGBRow = WebPMultARGBRowC;
  WebPMultRow = WebPMultRowC;
  WebPApplyAlphaMultiply = ApplyAlphaMultiply;
  WebPApplyAlphaMultiply4444 = ApplyAlphaMultiply_16b;

  WebPDispatchAlpha = DispatchAlpha_C;
  WebPDispatchAlphaToGreen = DispatchAlphaToGreen_C;
  WebPExtractAlpha = ExtractAlpha_C;
  WebPExtractGreen = ExtractGreen_C;

  // If defined, use CPUInfo() to overwrite some pointers with faster versions.
  if (VP8GetCPUInfo != NULL) {
#if defined(WEBP_USE_SSE2)
    if (VP8GetCPUInfo(kSSE2)) {
      WebPInitAlphaProcessingSSE2();
#if defined(WEBP_USE_SSE41)
      if (VP8GetCPUInfo(kSSE4_1)) {
        WebPInitAlphaProcessingSSE41();
      }
#endif
    }
#endif
#if defined(WEBP_USE_NEON)
    if (VP8GetCPUInfo(kNEON)) {
      WebPInitAlphaProcessingNEON();
    }
#endif
#if defined(WEBP_USE_MIPS_DSP_R2)
    if (VP8GetCPUInfo(kMIPSdspR2)) {
      WebPInitAlphaProcessingMIPSdspR2();
    }
#endif
  }
  alpha_processing_last_cpuinfo_used = VP8GetCPUInfo;
}