// Copyright 2011 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.

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

//

// functions for sample output.

//

// Author: Skal (pascal.massimino@gmail.com)

#include <assert.h>

#include <stdlib.h>

#include "src/dec/vp8i_dec.h"

#include "src/dec/webpi_dec.h"

#include "src/dsp/dsp.h"

#include "src/dsp/yuv.h"

#include "src/utils/utils.h"

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

// Main YUV<->RGB conversion functions

static int EmitYUV(const VP8Io* const io, WebPDecParams* const p) {

  WebPDecBuffer* output = p->output;

  const WebPYUVABuffer* const buf = &output->u.YUVA;

  uint8_t* const y_dst = buf->y + (size_t)io->mb_y * buf->y_stride;

  uint8_t* const u_dst = buf->u + (size_t)(io->mb_y >> 1) * buf->u_stride;

  uint8_t* const v_dst = buf->v + (size_t)(io->mb_y >> 1) * buf->v_stride;

  const int mb_w = io->mb_w;

  const int mb_h = io->mb_h;

  const int uv_w = (mb_w + 1) / 2;

  const int uv_h = (mb_h + 1) / 2;

  WebPCopyPlane(io->y, io->y_stride, y_dst, buf->y_stride, mb_w, mb_h);

  WebPCopyPlane(io->u, io->uv_stride, u_dst, buf->u_stride, uv_w, uv_h);

  WebPCopyPlane(io->v, io->uv_stride, v_dst, buf->v_stride, uv_w, uv_h);

  return io->mb_h;

}

// Point-sampling U/V sampler.

static int EmitSampledRGB(const VP8Io* const io, WebPDecParams* const p) {

  WebPDecBuffer* const output = p->output;

  WebPRGBABuffer* const buf = &output->u.RGBA;

  uint8_t* const dst = buf->rgba + (size_t)io->mb_y * buf->stride;

  WebPSamplerProcessPlane(io->y, io->y_stride,

                          io->u, io->v, io->uv_stride,

                          dst, buf->stride, io->mb_w, io->mb_h,

                          WebPSamplers[output->colorspace]);

  return io->mb_h;

}

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

// Fancy upsampling

#ifdef FANCY_UPSAMPLING

static int EmitFancyRGB(const VP8Io* const io, WebPDecParams* const p) {

  int num_lines_out = io->mb_h;   // a priori guess

  const WebPRGBABuffer* const buf = &p->output->u.RGBA;

  uint8_t* dst = buf->rgba + (size_t)io->mb_y * buf->stride;

  WebPUpsampleLinePairFunc upsample = WebPUpsamplers[p->output->colorspace];

  const uint8_t* cur_y = io->y;

  const uint8_t* cur_u = io->u;

  const uint8_t* cur_v = io->v;

  const uint8_t* top_u = p->tmp_u;

  const uint8_t* top_v = p->tmp_v;

  int y = io->mb_y;

  const int y_end = io->mb_y + io->mb_h;

  const int mb_w = io->mb_w;

  const int uv_w = (mb_w + 1) / 2;

  if (y == 0) {

    // First line is special cased. We mirror the u/v samples at boundary.

    upsample(cur_y, NULL, cur_u, cur_v, cur_u, cur_v, dst, NULL, mb_w);

  } else {

    // We can finish the left-over line from previous call.

    upsample(p->tmp_y, cur_y, top_u, top_v, cur_u, cur_v,

             dst - buf->stride, dst, mb_w);

    ++num_lines_out;

  }

  // Loop over each output pairs of row.

  for (; y + 2 < y_end; y += 2) {

    top_u = cur_u;

    top_v = cur_v;

    cur_u += io->uv_stride;

    cur_v += io->uv_stride;

    dst += 2 * buf->stride;

    cur_y += 2 * io->y_stride;

    upsample(cur_y - io->y_stride, cur_y,

             top_u, top_v, cur_u, cur_v,

             dst - buf->stride, dst, mb_w);

  }

  // move to last row

  cur_y += io->y_stride;

  if (io->crop_top + y_end < io->crop_bottom) {

    // Save the unfinished samples for next call (as we're not done yet).

    memcpy(p->tmp_y, cur_y, mb_w * sizeof(*p->tmp_y));

    memcpy(p->tmp_u, cur_u, uv_w * sizeof(*p->tmp_u));

    memcpy(p->tmp_v, cur_v, uv_w * sizeof(*p->tmp_v));

    // The fancy upsampler leaves a row unfinished behind

    // (except for the very last row)

    num_lines_out--;

  } else {

    // Process the very last row of even-sized picture

    if (!(y_end & 1)) {

      upsample(cur_y, NULL, cur_u, cur_v, cur_u, cur_v,

               dst + buf->stride, NULL, mb_w);

    }

  }

  return num_lines_out;

}

#endif    /* FANCY_UPSAMPLING */

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

static void FillAlphaPlane(uint8_t* dst, int w, int h, int stride) {

  int j;

  for (j = 0; j < h; ++j) {

    memset(dst, 0xff, w * sizeof(*dst));

    dst += stride;

  }

}

static int EmitAlphaYUV(const VP8Io* const io, WebPDecParams* const p,

                        int expected_num_lines_out) {

  const uint8_t* alpha = io->a;

  const WebPYUVABuffer* const buf = &p->output->u.YUVA;

  const int mb_w = io->mb_w;

  const int mb_h = io->mb_h;

  uint8_t* dst = buf->a + (size_t)io->mb_y * buf->a_stride;

  int j;

  (void)expected_num_lines_out;

  assert(expected_num_lines_out == mb_h);

  if (alpha != NULL) {

    for (j = 0; j < mb_h; ++j) {

      memcpy(dst, alpha, mb_w * sizeof(*dst));

      alpha += io->width;

      dst += buf->a_stride;

    }

  } else if (buf->a != NULL) {

    // the user requested alpha, but there is none, set it to opaque.

    FillAlphaPlane(dst, mb_w, mb_h, buf->a_stride);

  }

  return 0;

}

static int GetAlphaSourceRow(const VP8Io* const io,

                             const uint8_t** alpha, int* const num_rows) {

  int start_y = io->mb_y;

  *num_rows = io->mb_h;

  // Compensate for the 1-line delay of the fancy upscaler.

  // This is similar to EmitFancyRGB().

  if (io->fancy_upsampling) {

    if (start_y == 0) {

      // We don't process the last row yet. It'll be done during the next call.

      --*num_rows;

    } else {

      --start_y;

      // Fortunately, *alpha data is persistent, so we can go back

      // one row and finish alpha blending, now that the fancy upscaler

      // completed the YUV->RGB interpolation.

      *alpha -= io->width;

    }

    if (io->crop_top + io->mb_y + io->mb_h == io->crop_bottom) {

      // If it's the very last call, we process all the remaining rows!

      *num_rows = io->crop_bottom - io->crop_top - start_y;

    }

  }

  return start_y;

}

static int EmitAlphaRGB(const VP8Io* const io, WebPDecParams* const p,

                        int expected_num_lines_out) {

  const uint8_t* alpha = io->a;

  if (alpha != NULL) {

    const int mb_w = io->mb_w;

    const WEBP_CSP_MODE colorspace = p->output->colorspace;

    const int alpha_first =

        (colorspace == MODE_ARGB || colorspace == MODE_Argb);

    const WebPRGBABuffer* const buf = &p->output->u.RGBA;

    int num_rows;

    const size_t start_y = GetAlphaSourceRow(io, &alpha, &num_rows);

    uint8_t* const base_rgba = buf->rgba + start_y * buf->stride;

    uint8_t* const dst = base_rgba + (alpha_first ? 0 : 3);

    const int has_alpha = WebPDispatchAlpha(alpha, io->width, mb_w,

                                            num_rows, dst, buf->stride);

    (void)expected_num_lines_out;

    assert(expected_num_lines_out == num_rows);

    // has_alpha is true if there's non-trivial alpha to premultiply with.

    if (has_alpha && WebPIsPremultipliedMode(colorspace)) {

      WebPApplyAlphaMultiply(base_rgba, alpha_first,

                             mb_w, num_rows, buf->stride);

    }

  }

  return 0;

}

static int EmitAlphaRGBA4444(const VP8Io* const io, WebPDecParams* const p,

                             int expected_num_lines_out) {

  const uint8_t* alpha = io->a;

  if (alpha != NULL) {

    const int mb_w = io->mb_w;

    const WEBP_CSP_MODE colorspace = p->output->colorspace;

    const WebPRGBABuffer* const buf = &p->output->u.RGBA;

    int num_rows;

    const size_t start_y = GetAlphaSourceRow(io, &alpha, &num_rows);

    uint8_t* const base_rgba = buf->rgba + start_y * buf->stride;

#if (WEBP_SWAP_16BIT_CSP == 1)

    uint8_t* alpha_dst = base_rgba;

#else

    uint8_t* alpha_dst = base_rgba + 1;

#endif

    uint32_t alpha_mask = 0x0f;

    int i, j;

    for (j = 0; j < num_rows; ++j) {

      for (i = 0; i < mb_w; ++i) {

        // Fill in the alpha value (converted to 4 bits).

        const uint32_t alpha_value = alpha[i] >> 4;

        alpha_dst[2 * i] = (alpha_dst[2 * i] & 0xf0) | alpha_value;

        alpha_mask &= alpha_value;

      }

      alpha += io->width;

      alpha_dst += buf->stride;

    }

    (void)expected_num_lines_out;

    assert(expected_num_lines_out == num_rows);

    if (alpha_mask != 0x0f && WebPIsPremultipliedMode(colorspace)) {

      WebPApplyAlphaMultiply4444(base_rgba, mb_w, num_rows, buf->stride);

    }

  }

  return 0;

}

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

// YUV rescaling (no final RGB conversion needed)

#if !defined(WEBP_REDUCE_SIZE)

static int Rescale(const uint8_t* src, int src_stride,

                   int new_lines, WebPRescaler* const wrk) {

  int num_lines_out = 0;

  while (new_lines > 0) {    // import new contributions of source rows.

    const int lines_in = WebPRescalerImport(wrk, new_lines, src, src_stride);

    src += lines_in * src_stride;

    new_lines -= lines_in;

    num_lines_out += WebPRescalerExport(wrk);    // emit output row(s)

  }

  return num_lines_out;

}

static int EmitRescaledYUV(const VP8Io* const io, WebPDecParams* const p) {

  const int mb_h = io->mb_h;

  const int uv_mb_h = (mb_h + 1) >> 1;

  WebPRescaler* const scaler = p->scaler_y;

  int num_lines_out = 0;

  if (WebPIsAlphaMode(p->output->colorspace) && io->a != NULL) {

    // Before rescaling, we premultiply the luma directly into the io->y

    // internal buffer. This is OK since these samples are not used for

    // intra-prediction (the top samples are saved in cache_y_/u_/v_).

    // But we need to cast the const away, though.

    WebPMultRows((uint8_t*)io->y, io->y_stride,

                 io->a, io->width, io->mb_w, mb_h, 0);

  }

  num_lines_out = Rescale(io->y, io->y_stride, mb_h, scaler);

  Rescale(io->u, io->uv_stride, uv_mb_h, p->scaler_u);

  Rescale(io->v, io->uv_stride, uv_mb_h, p->scaler_v);

  return num_lines_out;

}

static int EmitRescaledAlphaYUV(const VP8Io* const io, WebPDecParams* const p,

                                int expected_num_lines_out) {

  const WebPYUVABuffer* const buf = &p->output->u.YUVA;

  uint8_t* const dst_a = buf->a + (size_t)p->last_y * buf->a_stride;

  if (io->a != NULL) {

    uint8_t* const dst_y = buf->y + (size_t)p->last_y * buf->y_stride;

    const int num_lines_out = Rescale(io->a, io->width, io->mb_h, p->scaler_a);

    assert(expected_num_lines_out == num_lines_out);

    if (num_lines_out > 0) {   // unmultiply the Y

      WebPMultRows(dst_y, buf->y_stride, dst_a, buf->a_stride,

                   p->scaler_a->dst_width, num_lines_out, 1);

    }

  } else if (buf->a != NULL) {

    // the user requested alpha, but there is none, set it to opaque.

    assert(p->last_y + expected_num_lines_out <= io->scaled_height);

    FillAlphaPlane(dst_a, io->scaled_width, expected_num_lines_out,

                   buf->a_stride);

  }

  return 0;

}

static int InitYUVRescaler(const VP8Io* const io, WebPDecParams* const p) {

  const int has_alpha = WebPIsAlphaMode(p->output->colorspace);

  const WebPYUVABuffer* const buf = &p->output->u.YUVA;

  const int out_width  = io->scaled_width;

  const int out_height = io->scaled_height;

  const int uv_out_width  = (out_width + 1) >> 1;

  const int uv_out_height = (out_height + 1) >> 1;

  const int uv_in_width  = (io->mb_w + 1) >> 1;

  const int uv_in_height = (io->mb_h + 1) >> 1;

  // scratch memory for luma rescaler

  const size_t work_size = 2 * (size_t)out_width;

  const size_t uv_work_size = 2 * uv_out_width;  // and for each u/v ones

  uint64_t total_size;

  size_t rescaler_size;

  rescaler_t* work;

  WebPRescaler* scalers;

  const int num_rescalers = has_alpha ? 4 : 3;

  total_size = ((uint64_t)work_size + 2 * uv_work_size) * sizeof(*work);

  if (has_alpha) {

    total_size += (uint64_t)work_size * sizeof(*work);

  }

  rescaler_size = num_rescalers * sizeof(*p->scaler_y) + WEBP_ALIGN_CST;

  total_size += rescaler_size;

  if (!CheckSizeOverflow(total_size)) {

    return 0;

  }

  p->memory = WebPSafeMalloc(1ULL, (size_t)total_size);

  if (p->memory == NULL) {

    return 0;   // memory error

  }

  work = (rescaler_t*)p->memory;

  scalers = (WebPRescaler*)WEBP_ALIGN(

      (const uint8_t*)work + total_size - rescaler_size);

  p->scaler_y = &scalers[0];

  p->scaler_u = &scalers[1];

  p->scaler_v = &scalers[2];

  p->scaler_a = has_alpha ? &scalers[3] : NULL;

  if (!WebPRescalerInit(p->scaler_y, io->mb_w, io->mb_h,

                        buf->y, out_width, out_height, buf->y_stride, 1,

                        work) ||

      !WebPRescalerInit(p->scaler_u, uv_in_width, uv_in_height,

                        buf->u, uv_out_width, uv_out_height, buf->u_stride, 1,

                        work + work_size) ||

      !WebPRescalerInit(p->scaler_v, uv_in_width, uv_in_height,

                        buf->v, uv_out_width, uv_out_height, buf->v_stride, 1,

                        work + work_size + uv_work_size)) {

    return 0;

  }

  p->emit = EmitRescaledYUV;

  if (has_alpha) {

    if (!WebPRescalerInit(p->scaler_a, io->mb_w, io->mb_h,

                          buf->a, out_width, out_height, buf->a_stride, 1,

                          work + work_size + 2 * uv_work_size)) {

      return 0;

    }

    p->emit_alpha = EmitRescaledAlphaYUV;

    WebPInitAlphaProcessing();

  }

  return 1;

}

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

// RGBA rescaling

static int ExportRGB(WebPDecParams* const p, int y_pos) {

  const WebPYUV444Converter convert =

      WebPYUV444Converters[p->output->colorspace];

  const WebPRGBABuffer* const buf = &p->output->u.RGBA;

  uint8_t* dst = buf->rgba + (size_t)y_pos * buf->stride;

  int num_lines_out = 0;

  // For RGB rescaling, because of the YUV420, current scan position

  // U/V can be +1/-1 line from the Y one.  Hence the double test.

  while (WebPRescalerHasPendingOutput(p->scaler_y) &&

         WebPRescalerHasPendingOutput(p->scaler_u)) {

    assert(y_pos + num_lines_out < p->output->height);

    assert(p->scaler_u->y_accum == p->scaler_v->y_accum);

    WebPRescalerExportRow(p->scaler_y);

    WebPRescalerExportRow(p->scaler_u);

    WebPRescalerExportRow(p->scaler_v);

    convert(p->scaler_y->dst, p->scaler_u->dst, p->scaler_v->dst,

            dst, p->scaler_y->dst_width);

    dst += buf->stride;

    ++num_lines_out;

  }

  return num_lines_out;

}

static int EmitRescaledRGB(const VP8Io* const io, WebPDecParams* const p) {

  const int mb_h = io->mb_h;

  const int uv_mb_h = (mb_h + 1) >> 1;

  int j = 0, uv_j = 0;

  int num_lines_out = 0;

  while (j < mb_h) {

    const int y_lines_in =

        WebPRescalerImport(p->scaler_y, mb_h - j,

                           io->y + (size_t)j * io->y_stride, io->y_stride);

    j += y_lines_in;

    if (WebPRescaleNeededLines(p->scaler_u, uv_mb_h - uv_j)) {

      const int u_lines_in = WebPRescalerImport(

          p->scaler_u, uv_mb_h - uv_j, io->u + (size_t)uv_j * io->uv_stride,

          io->uv_stride);

      const int v_lines_in = WebPRescalerImport(

          p->scaler_v, uv_mb_h - uv_j, io->v + (size_t)uv_j * io->uv_stride,

          io->uv_stride);

      (void)v_lines_in;   // remove a gcc warning

      assert(u_lines_in == v_lines_in);

      uv_j += u_lines_in;

    }

    num_lines_out += ExportRGB(p, p->last_y + num_lines_out);

  }

  return num_lines_out;

}

static int ExportAlpha(WebPDecParams* const p, int y_pos, int max_lines_out) {

  const WebPRGBABuffer* const buf = &p->output->u.RGBA;

  uint8_t* const base_rgba = buf->rgba + (size_t)y_pos * buf->stride;

  const WEBP_CSP_MODE colorspace = p->output->colorspace;

  const int alpha_first =

      (colorspace == MODE_ARGB || colorspace == MODE_Argb);

  uint8_t* dst = base_rgba + (alpha_first ? 0 : 3);

  int num_lines_out = 0;

  const int is_premult_alpha = WebPIsPremultipliedMode(colorspace);

  uint32_t non_opaque = 0;

  const int width = p->scaler_a->dst_width;

  while (WebPRescalerHasPendingOutput(p->scaler_a) &&

         num_lines_out < max_lines_out) {

    assert(y_pos + num_lines_out < p->output->height);

    WebPRescalerExportRow(p->scaler_a);

    non_opaque |= WebPDispatchAlpha(p->scaler_a->dst, 0, width, 1, dst, 0);

    dst += buf->stride;

    ++num_lines_out;

  }

  if (is_premult_alpha && non_opaque) {

    WebPApplyAlphaMultiply(base_rgba, alpha_first,

                           width, num_lines_out, buf->stride);

  }

  return num_lines_out;

}

static int ExportAlphaRGBA4444(WebPDecParams* const p, int y_pos,

                               int max_lines_out) {

  const WebPRGBABuffer* const buf = &p->output->u.RGBA;

  uint8_t* const base_rgba = buf->rgba + (size_t)y_pos * buf->stride;

#if (WEBP_SWAP_16BIT_CSP == 1)

  uint8_t* alpha_dst = base_rgba;

#else

  uint8_t* alpha_dst = base_rgba + 1;

#endif

  int num_lines_out = 0;

  const WEBP_CSP_MODE colorspace = p->output->colorspace;

  const int width = p->scaler_a->dst_width;

  const int is_premult_alpha = WebPIsPremultipliedMode(colorspace);

  uint32_t alpha_mask = 0x0f;

  while (WebPRescalerHasPendingOutput(p->scaler_a) &&

         num_lines_out < max_lines_out) {

    int i;

    assert(y_pos + num_lines_out < p->output->height);

    WebPRescalerExportRow(p->scaler_a);

    for (i = 0; i < width; ++i) {

      // Fill in the alpha value (converted to 4 bits).

      const uint32_t alpha_value = p->scaler_a->dst[i] >> 4;

      alpha_dst[2 * i] = (alpha_dst[2 * i] & 0xf0) | alpha_value;

      alpha_mask &= alpha_value;

    }

    alpha_dst += buf->stride;

    ++num_lines_out;

  }

  if (is_premult_alpha && alpha_mask != 0x0f) {

    WebPApplyAlphaMultiply4444(base_rgba, width, num_lines_out, buf->stride);

  }

  return num_lines_out;

}

static int EmitRescaledAlphaRGB(const VP8Io* const io, WebPDecParams* const p,

                                int expected_num_out_lines) {

  if (io->a != NULL) {

    WebPRescaler* const scaler = p->scaler_a;

    int lines_left = expected_num_out_lines;

    const int y_end = p->last_y + lines_left;

    while (lines_left > 0) {

      const int64_t row_offset = (int64_t)scaler->src_y - io->mb_y;

      WebPRescalerImport(scaler, io->mb_h + io->mb_y - scaler->src_y,

                         io->a + row_offset * io->width, io->width);

      lines_left -= p->emit_alpha_row(p, y_end - lines_left, lines_left);

    }

  }

  return 0;

}

static int InitRGBRescaler(const VP8Io* const io, WebPDecParams* const p) {

  const int has_alpha = WebPIsAlphaMode(p->output->colorspace);

  const int out_width  = io->scaled_width;

  const int out_height = io->scaled_height;

  const int uv_in_width  = (io->mb_w + 1) >> 1;

  const int uv_in_height = (io->mb_h + 1) >> 1;

  // scratch memory for one rescaler

  const size_t work_size = 2 * (size_t)out_width;

  rescaler_t* work;  // rescalers work area

  uint8_t* tmp;   // tmp storage for scaled YUV444 samples before RGB conversion

  uint64_t tmp_size1, tmp_size2, total_size;

  size_t rescaler_size;

  WebPRescaler* scalers;

  const int num_rescalers = has_alpha ? 4 : 3;

  tmp_size1 = (uint64_t)num_rescalers * work_size;

  tmp_size2 = (uint64_t)num_rescalers * out_width;

  total_size = tmp_size1 * sizeof(*work) + tmp_size2 * sizeof(*tmp);

  rescaler_size = num_rescalers * sizeof(*p->scaler_y) + WEBP_ALIGN_CST;

  total_size += rescaler_size;

  if (!CheckSizeOverflow(total_size)) {

    return 0;

  }

  p->memory = WebPSafeMalloc(1ULL, (size_t)total_size);

  if (p->memory == NULL) {

    return 0;   // memory error

  }

  work = (rescaler_t*)p->memory;

  tmp = (uint8_t*)(work + tmp_size1);

  scalers = (WebPRescaler*)WEBP_ALIGN(

      (const uint8_t*)work + total_size - rescaler_size);

  p->scaler_y = &scalers[0];

  p->scaler_u = &scalers[1];

  p->scaler_v = &scalers[2];

  p->scaler_a = has_alpha ? &scalers[3] : NULL;

  if (!WebPRescalerInit(p->scaler_y, io->mb_w, io->mb_h,

                        tmp + 0 * out_width, out_width, out_height, 0, 1,

                        work + 0 * work_size) ||

      !WebPRescalerInit(p->scaler_u, uv_in_width, uv_in_height,

                        tmp + 1 * out_width, out_width, out_height, 0, 1,

                        work + 1 * work_size) ||

      !WebPRescalerInit(p->scaler_v, uv_in_width, uv_in_height,

                        tmp + 2 * out_width, out_width, out_height, 0, 1,

                        work + 2 * work_size)) {

    return 0;

  }

  p->emit = EmitRescaledRGB;

  WebPInitYUV444Converters();

  if (has_alpha) {

    if (!WebPRescalerInit(p->scaler_a, io->mb_w, io->mb_h,

                          tmp + 3 * out_width, out_width, out_height, 0, 1,

                          work + 3 * work_size)) {

      return 0;

    }

    p->emit_alpha = EmitRescaledAlphaRGB;

    if (p->output->colorspace == MODE_RGBA_4444 ||

        p->output->colorspace == MODE_rgbA_4444) {

      p->emit_alpha_row = ExportAlphaRGBA4444;

    } else {

      p->emit_alpha_row = ExportAlpha;

    }

    WebPInitAlphaProcessing();

  }

  return 1;

}

#endif  // WEBP_REDUCE_SIZE

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

// Default custom functions

static int CustomSetup(VP8Io* io) {

  WebPDecParams* const p = (WebPDecParams*)io->opaque;

  const WEBP_CSP_MODE colorspace = p->output->colorspace;

  const int is_rgb = WebPIsRGBMode(colorspace);

  const int is_alpha = WebPIsAlphaMode(colorspace);

  p->memory = NULL;

  p->emit = NULL;

  p->emit_alpha = NULL;

  p->emit_alpha_row = NULL;

  if (!WebPIoInitFromOptions(p->options, io, is_alpha ? MODE_YUV : MODE_YUVA)) {

    return 0;

  }

  if (is_alpha && WebPIsPremultipliedMode(colorspace)) {

    WebPInitUpsamplers();

  }

  if (io->use_scaling) {

#if !defined(WEBP_REDUCE_SIZE)

    const int ok = is_rgb ? InitRGBRescaler(io, p) : InitYUVRescaler(io, p);

    if (!ok) {

      return 0;    // memory error

    }

#else

    return 0;   // rescaling support not compiled

#endif

  } else {

    if (is_rgb) {

      WebPInitSamplers();

      p->emit = EmitSampledRGB;   // default

      if (io->fancy_upsampling) {

#ifdef FANCY_UPSAMPLING

        const int uv_width = (io->mb_w + 1) >> 1;

        p->memory = WebPSafeMalloc(1ULL, (size_t)(io->mb_w + 2 * uv_width));

        if (p->memory == NULL) {

          return 0;   // memory error.

        }

        p->tmp_y = (uint8_t*)p->memory;

        p->tmp_u = p->tmp_y + io->mb_w;

        p->tmp_v = p->tmp_u + uv_width;

        p->emit = EmitFancyRGB;

        WebPInitUpsamplers();

#endif

      }

    } else {

      p->emit = EmitYUV;

    }

    if (is_alpha) {  // need transparency output

      p->emit_alpha =

          (colorspace == MODE_RGBA_4444 || colorspace == MODE_rgbA_4444) ?

              EmitAlphaRGBA4444

          : is_rgb ? EmitAlphaRGB

          : EmitAlphaYUV;

      if (is_rgb) {

        WebPInitAlphaProcessing();

      }

    }

  }

  return 1;

}

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

static int CustomPut(const VP8Io* io) {

  WebPDecParams* const p = (WebPDecParams*)io->opaque;

  const int mb_w = io->mb_w;

  const int mb_h = io->mb_h;

  int num_lines_out;

  assert(!(io->mb_y & 1));

  if (mb_w <= 0 || mb_h <= 0) {

    return 0;

  }

  num_lines_out = p->emit(io, p);

  if (p->emit_alpha != NULL) {

    p->emit_alpha(io, p, num_lines_out);

  }

  p->last_y += num_lines_out;

  return 1;

}

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

static void CustomTeardown(const VP8Io* io) {

  WebPDecParams* const p = (WebPDecParams*)io->opaque;

  WebPSafeFree(p->memory);

  p->memory = NULL;

}

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

// Main entry point

void WebPInitCustomIo(WebPDecParams* const params, VP8Io* const io) {

  io->put      = CustomPut;

  io->setup    = CustomSetup;

  io->teardown = CustomTeardown;

  io->opaque   = params;

}

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