alpha_processing.c

// 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 ([email protected])

#include <assert.h>
#include <stddef.h>

#include "src/dsp/cpu.h"
#include "src/dsp/dsp.h"
#include "src/webp/types.h"

// Tables can be faster on some platform but incur some extra binary size (~2k).
#if !defined(USE_TABLES_FOR_ALPHA_MULT)
#define USE_TABLES_FOR_ALPHA_MULT 0   // ALTERNATE_CODE
#endif


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

#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;
}

#if (USE_TABLES_FOR_ALPHA_MULT == 1)

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 WebPMultARGBRow_C(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 WebPMultRow_C(uint8_t* WEBP_RESTRICT const ptr,
                   const uint8_t* WEBP_RESTRICT 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* WEBP_RESTRICT const ptr,
                    const uint8_t* WEBP_RESTRICT 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* WEBP_RESTRICT ptr, int stride,
                  const uint8_t* WEBP_RESTRICT 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

#if !WEBP_NEON_OMIT_C_CODE
static void ApplyAlphaMultiply_C(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;
  }
}
#endif  // !WEBP_NEON_OMIT_C_CODE
#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_C(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_C(uint8_t* rgba4444,
                                     int w, int h, int stride) {
#if (WEBP_SWAP_16BIT_CSP == 1)
  ApplyAlphaMultiply4444_C(rgba4444, w, h, stride, 1);
#else
  ApplyAlphaMultiply4444_C(rgba4444, w, h, stride, 0);
#endif
}

#if !WEBP_NEON_OMIT_C_CODE
static int DispatchAlpha_C(const uint8_t* WEBP_RESTRICT alpha, int alpha_stride,
                           int width, int height,
                           uint8_t* WEBP_RESTRICT 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* WEBP_RESTRICT alpha,
                                   int alpha_stride, int width, int height,
                                   uint32_t* WEBP_RESTRICT 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* WEBP_RESTRICT argb, int argb_stride,
                          int width, int height,
                          uint8_t* WEBP_RESTRICT 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* WEBP_RESTRICT argb,
                           uint8_t* WEBP_RESTRICT alpha, int size) {
  int i;
  for (i = 0; i < size; ++i) alpha[i] = argb[i] >> 8;
}
#endif  // !WEBP_NEON_OMIT_C_CODE

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

static int HasAlpha8b_C(const uint8_t* src, int length) {
  while (length-- > 0) if (*src++ != 0xff) return 1;
  return 0;
}

static int HasAlpha32b_C(const uint8_t* src, int length) {
  int x;
  for (x = 0; length-- > 0; x += 4) if (src[x] != 0xff) return 1;
  return 0;
}

static void AlphaReplace_C(uint32_t* src, int length, uint32_t color) {
  int x;
  for (x = 0; x < length; ++x) if ((src[x] >> 24) == 0) src[x] = color;
}

//------------------------------------------------------------------------------
// Simple channel manipulations.

static WEBP_INLINE uint32_t MakeARGB32(int a, int r, int g, int b) {
  return (((uint32_t)a << 24) | (r << 16) | (g << 8) | b);
}

#ifdef WORDS_BIGENDIAN
static void PackARGB_C(const uint8_t* WEBP_RESTRICT a,
                       const uint8_t* WEBP_RESTRICT r,
                       const uint8_t* WEBP_RESTRICT g,
                       const uint8_t* WEBP_RESTRICT b,
                       int len, uint32_t* WEBP_RESTRICT out) {
  int i;
  for (i = 0; i < len; ++i) {
    out[i] = MakeARGB32(a[4 * i], r[4 * i], g[4 * i], b[4 * i]);
  }
}
#endif

static void PackRGB_C(const uint8_t* WEBP_RESTRICT r,
                      const uint8_t* WEBP_RESTRICT g,
                      const uint8_t* WEBP_RESTRICT b,
                      int len, int step, uint32_t* WEBP_RESTRICT out) {
  int i, offset = 0;
  for (i = 0; i < len; ++i) {
    out[i] = MakeARGB32(0xff, r[offset], g[offset], b[offset]);
    offset += step;
  }
}

void (*WebPApplyAlphaMultiply)(uint8_t*, int, int, int, int);
void (*WebPApplyAlphaMultiply4444)(uint8_t*, int, int, int);
int (*WebPDispatchAlpha)(const uint8_t* WEBP_RESTRICT, int, int, int,
                         uint8_t* WEBP_RESTRICT, int);
void (*WebPDispatchAlphaToGreen)(const uint8_t* WEBP_RESTRICT, int, int, int,
                                 uint32_t* WEBP_RESTRICT, int);
int (*WebPExtractAlpha)(const uint8_t* WEBP_RESTRICT, int, int, int,
                        uint8_t* WEBP_RESTRICT, int);
void (*WebPExtractGreen)(const uint32_t* WEBP_RESTRICT argb,
                         uint8_t* WEBP_RESTRICT alpha, int size);
#ifdef WORDS_BIGENDIAN
void (*WebPPackARGB)(const uint8_t* a, const uint8_t* r, const uint8_t* g,
                     const uint8_t* b, int, uint32_t*);
#endif
void (*WebPPackRGB)(const uint8_t* WEBP_RESTRICT r,
                    const uint8_t* WEBP_RESTRICT g,
                    const uint8_t* WEBP_RESTRICT b,
                    int len, int step, uint32_t* WEBP_RESTRICT out);

int (*WebPHasAlpha8b)(const uint8_t* src, int length);
int (*WebPHasAlpha32b)(const uint8_t* src, int length);
void (*WebPAlphaReplace)(uint32_t* src, int length, uint32_t color);

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

extern VP8CPUInfo VP8GetCPUInfo;
extern void WebPInitAlphaProcessingMIPSdspR2(void);
extern void WebPInitAlphaProcessingSSE2(void);
extern void WebPInitAlphaProcessingSSE41(void);
extern void WebPInitAlphaProcessingNEON(void);

WEBP_DSP_INIT_FUNC(WebPInitAlphaProcessing) {
  WebPMultARGBRow = WebPMultARGBRow_C;
  WebPMultRow = WebPMultRow_C;
  WebPApplyAlphaMultiply4444 = ApplyAlphaMultiply_16b_C;

#ifdef WORDS_BIGENDIAN
  WebPPackARGB = PackARGB_C;
#endif
  WebPPackRGB = PackRGB_C;
#if !WEBP_NEON_OMIT_C_CODE
  WebPApplyAlphaMultiply = ApplyAlphaMultiply_C;
  WebPDispatchAlpha = DispatchAlpha_C;
  WebPDispatchAlphaToGreen = DispatchAlphaToGreen_C;
  WebPExtractAlpha = ExtractAlpha_C;
  WebPExtractGreen = ExtractGreen_C;
#endif

  WebPHasAlpha8b = HasAlpha8b_C;
  WebPHasAlpha32b = HasAlpha32b_C;
  WebPAlphaReplace = AlphaReplace_C;

  // If defined, use CPUInfo() to overwrite some pointers with faster versions.
  if (VP8GetCPUInfo != NULL) {
#if defined(WEBP_HAVE_SSE2)
    if (VP8GetCPUInfo(kSSE2)) {
      WebPInitAlphaProcessingSSE2();
#if defined(WEBP_HAVE_SSE41)
      if (VP8GetCPUInfo(kSSE4_1)) {
        WebPInitAlphaProcessingSSE41();
      }
#endif
    }
#endif
#if defined(WEBP_USE_MIPS_DSP_R2)
    if (VP8GetCPUInfo(kMIPSdspR2)) {
      WebPInitAlphaProcessingMIPSdspR2();
    }
#endif
  }

#if defined(WEBP_HAVE_NEON)
  if (WEBP_NEON_OMIT_C_CODE ||
      (VP8GetCPUInfo != NULL && VP8GetCPUInfo(kNEON))) {
    WebPInitAlphaProcessingNEON();
  }
#endif

  assert(WebPMultARGBRow != NULL);
  assert(WebPMultRow != NULL);
  assert(WebPApplyAlphaMultiply != NULL);
  assert(WebPApplyAlphaMultiply4444 != NULL);
  assert(WebPDispatchAlpha != NULL);
  assert(WebPDispatchAlphaToGreen != NULL);
  assert(WebPExtractAlpha != NULL);
  assert(WebPExtractGreen != NULL);
#ifdef WORDS_BIGENDIAN
  assert(WebPPackARGB != NULL);
#endif
  assert(WebPPackRGB != NULL);
  assert(WebPHasAlpha8b != NULL);
  assert(WebPHasAlpha32b != NULL);
  assert(WebPAlphaReplace != NULL);
}