// 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.

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

//

// Alpha-plane compression.

//

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

#include <assert.h>

#include <stdlib.h>

#include "src/enc/vp8i_enc.h"

#include "src/dsp/dsp.h"

#include "src/utils/filters_utils.h"

#include "src/utils/quant_levels_utils.h"

#include "src/utils/utils.h"

#include "src/webp/format_constants.h"

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

// Encodes the given alpha data via specified compression method 'method'.

// The pre-processing (quantization) is performed if 'quality' is less than 100.

// For such cases, the encoding is lossy. The valid range is [0, 100] for

// 'quality' and [0, 1] for 'method':

//   'method = 0' - No compression;

//   'method = 1' - Use lossless coder on the alpha plane only

// 'filter' values [0, 4] correspond to prediction modes none, horizontal,

// vertical & gradient filters. The prediction mode 4 will try all the

// prediction modes 0 to 3 and pick the best one.

// 'effort_level': specifies how much effort must be spent to try and reduce

//  the compressed output size. In range 0 (quick) to 6 (slow).

//

// 'output' corresponds to the buffer containing compressed alpha data.

//          This buffer is allocated by this method and caller should call

//          WebPSafeFree(*output) when done.

// 'output_size' corresponds to size of this compressed alpha buffer.

//

// Returns 1 on successfully encoding the alpha and

//         0 if either:

//           invalid quality or method, or

//           memory allocation for the compressed data fails.

#include "src/enc/vp8li_enc.h"

static int EncodeLossless(const uint8_t* const data, int width, int height,

                          int effort_level,  // in [0..6] range

                          int use_quality_100, VP8LBitWriter* const bw,

                          WebPAuxStats* const stats) {

  int ok = 0;

  WebPConfig config;

  WebPPicture picture;

  WebPPictureInit(&picture);

  picture.width = width;

  picture.height = height;

  picture.use_argb = 1;

  picture.stats = stats;

  if (!WebPPictureAlloc(&picture)) return 0;

  // Transfer the alpha values to the green channel.

  WebPDispatchAlphaToGreen(data, width, picture.width, picture.height,

                           picture.argb, picture.argb_stride);

  WebPConfigInit(&config);

  config.lossless = 1;

  // Enable exact, or it would alter RGB values of transparent alpha, which is

  // normally OK but not here since we are not encoding the input image but  an

  // internal encoding-related image containing necessary exact information in

  // RGB channels.

  config.exact = 1;

  config.method = effort_level;  // impact is very small

  // Set a low default quality for encoding alpha. Ensure that Alpha quality at

  // lower methods (3 and below) is less than the threshold for triggering

  // costly 'BackwardReferencesTraceBackwards'.

  // If the alpha quality is set to 100 and the method to 6, allow for a high

  // lossless quality to trigger the cruncher.

  config.quality =

      (use_quality_100 && effort_level == 6) ? 100 : 8.f * effort_level;

  assert(config.quality >= 0 && config.quality <= 100.f);

  // TODO(urvang): Temporary fix to avoid generating images that trigger

  // a decoder bug related to alpha with color cache.

  // See: https://code.google.com/p/webp/issues/detail?id=239

  // Need to re-enable this later.

  ok = (VP8LEncodeStream(&config, &picture, bw, 0 /*use_cache*/) == VP8_ENC_OK);

  WebPPictureFree(&picture);

  ok = ok && !bw->error_;

  if (!ok) {

    VP8LBitWriterWipeOut(bw);

    return 0;

  }

  return 1;

}

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

// Small struct to hold the result of a filter mode compression attempt.

typedef struct {

  size_t score;

  VP8BitWriter bw;

  WebPAuxStats stats;

} FilterTrial;

// This function always returns an initialized 'bw' object, even upon error.

static int EncodeAlphaInternal(const uint8_t* const data, int width, int height,

                               int method, int filter, int reduce_levels,

                               int effort_level,  // in [0..6] range

                               uint8_t* const tmp_alpha,

                               FilterTrial* result) {

  int ok = 0;

  const uint8_t* alpha_src;

  WebPFilterFunc filter_func;

  uint8_t header;

  const size_t data_size = width * height;

  const uint8_t* output = NULL;

  size_t output_size = 0;

  VP8LBitWriter tmp_bw;

  assert((uint64_t)data_size == (uint64_t)width * height);  // as per spec

  assert(filter >= 0 && filter < WEBP_FILTER_LAST);

  assert(method >= ALPHA_NO_COMPRESSION);

  assert(method <= ALPHA_LOSSLESS_COMPRESSION);

  assert(sizeof(header) == ALPHA_HEADER_LEN);

  filter_func = WebPFilters[filter];

  if (filter_func != NULL) {

    filter_func(data, width, height, width, tmp_alpha);

    alpha_src = tmp_alpha;

  }  else {

    alpha_src = data;

  }

  if (method != ALPHA_NO_COMPRESSION) {

    ok = VP8LBitWriterInit(&tmp_bw, data_size >> 3);

    ok = ok && EncodeLossless(alpha_src, width, height, effort_level,

                              !reduce_levels, &tmp_bw, &result->stats);

    if (ok) {

      output = VP8LBitWriterFinish(&tmp_bw);

      output_size = VP8LBitWriterNumBytes(&tmp_bw);

      if (output_size > data_size) {

        // compressed size is larger than source! Revert to uncompressed mode.

        method = ALPHA_NO_COMPRESSION;

        VP8LBitWriterWipeOut(&tmp_bw);

      }

    } else {

      VP8LBitWriterWipeOut(&tmp_bw);

      return 0;

    }

  }

  if (method == ALPHA_NO_COMPRESSION) {

    output = alpha_src;

    output_size = data_size;

    ok = 1;

  }

  // Emit final result.

  header = method | (filter << 2);

  if (reduce_levels) header |= ALPHA_PREPROCESSED_LEVELS << 4;

  VP8BitWriterInit(&result->bw, ALPHA_HEADER_LEN + output_size);

  ok = ok && VP8BitWriterAppend(&result->bw, &header, ALPHA_HEADER_LEN);

  ok = ok && VP8BitWriterAppend(&result->bw, output, output_size);

  if (method != ALPHA_NO_COMPRESSION) {

    VP8LBitWriterWipeOut(&tmp_bw);

  }

  ok = ok && !result->bw.error_;

  result->score = VP8BitWriterSize(&result->bw);

  return ok;

}

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

static int GetNumColors(const uint8_t* data, int width, int height,

                        int stride) {

  int j;

  int colors = 0;

  uint8_t color[256] = { 0 };

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

    int i;

    const uint8_t* const p = data + j * stride;

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

      color[p[i]] = 1;

    }

  }

  for (j = 0; j < 256; ++j) {

    if (color[j] > 0) ++colors;

  }

  return colors;

}

#define FILTER_TRY_NONE (1 << WEBP_FILTER_NONE)

#define FILTER_TRY_ALL ((1 << WEBP_FILTER_LAST) - 1)

// Given the input 'filter' option, return an OR'd bit-set of filters to try.

static uint32_t GetFilterMap(const uint8_t* alpha, int width, int height,

                             int filter, int effort_level) {

  uint32_t bit_map = 0U;

  if (filter == WEBP_FILTER_FAST) {

    // Quick estimate of the best candidate.

    int try_filter_none = (effort_level > 3);

    const int kMinColorsForFilterNone = 16;

    const int kMaxColorsForFilterNone = 192;

    const int num_colors = GetNumColors(alpha, width, height, width);

    // For low number of colors, NONE yields better compression.

    filter = (num_colors <= kMinColorsForFilterNone)

        ? WEBP_FILTER_NONE

        : WebPEstimateBestFilter(alpha, width, height, width);

    bit_map |= 1 << filter;

    // For large number of colors, try FILTER_NONE in addition to the best

    // filter as well.

    if (try_filter_none || num_colors > kMaxColorsForFilterNone) {

      bit_map |= FILTER_TRY_NONE;

    }

  } else if (filter == WEBP_FILTER_NONE) {

    bit_map = FILTER_TRY_NONE;

  } else {  // WEBP_FILTER_BEST -> try all

    bit_map = FILTER_TRY_ALL;

  }

  return bit_map;

}

static void InitFilterTrial(FilterTrial* const score) {

  score->score = (size_t)~0U;

  VP8BitWriterInit(&score->bw, 0);

}

static int ApplyFiltersAndEncode(const uint8_t* alpha, int width, int height,

                                 size_t data_size, int method, int filter,

                                 int reduce_levels, int effort_level,

                                 uint8_t** const output,

                                 size_t* const output_size,

                                 WebPAuxStats* const stats) {

  int ok = 1;

  FilterTrial best;

  uint32_t try_map =

      GetFilterMap(alpha, width, height, filter, effort_level);

  InitFilterTrial(&best);

  if (try_map != FILTER_TRY_NONE) {

    uint8_t* filtered_alpha =  (uint8_t*)WebPSafeMalloc(1ULL, data_size);

    if (filtered_alpha == NULL) return 0;

    for (filter = WEBP_FILTER_NONE; ok && try_map; ++filter, try_map >>= 1) {

      if (try_map & 1) {

        FilterTrial trial;

        ok = EncodeAlphaInternal(alpha, width, height, method, filter,

                                 reduce_levels, effort_level, filtered_alpha,

                                 &trial;;

        if (ok && trial.score < best.score) {

          VP8BitWriterWipeOut(&best.bw);

          best = trial;

        } else {

          VP8BitWriterWipeOut(&trial.bw);

        }

      }

    }

    WebPSafeFree(filtered_alpha);

  } else {

    ok = EncodeAlphaInternal(alpha, width, height, method, WEBP_FILTER_NONE,

                             reduce_levels, effort_level, NULL, &best);

  }

  if (ok) {

#if !defined(WEBP_DISABLE_STATS)

    if (stats != NULL) {

      stats->lossless_features = best.stats.lossless_features;

      stats->histogram_bits = best.stats.histogram_bits;

      stats->transform_bits = best.stats.transform_bits;

      stats->cache_bits = best.stats.cache_bits;

      stats->palette_size = best.stats.palette_size;

      stats->lossless_size = best.stats.lossless_size;

      stats->lossless_hdr_size = best.stats.lossless_hdr_size;

      stats->lossless_data_size = best.stats.lossless_data_size;

    }

#else

    (void)stats;

#endif

    *output_size = VP8BitWriterSize(&best.bw);

    *output = VP8BitWriterBuf(&best.bw);

  } else {

    VP8BitWriterWipeOut(&best.bw);

  }

  return ok;

}

static int EncodeAlpha(VP8Encoder* const enc,

                       int quality, int method, int filter,

                       int effort_level,

                       uint8_t** const output, size_t* const output_size) {

  const WebPPicture* const pic = enc->pic_;

  const int width = pic->width;

  const int height = pic->height;

  uint8_t* quant_alpha = NULL;

  const size_t data_size = width * height;

  uint64_t sse = 0;

  int ok = 1;

  const int reduce_levels = (quality < 100);

  // quick sanity checks

  assert((uint64_t)data_size == (uint64_t)width * height);  // as per spec

  assert(enc != NULL && pic != NULL && pic->a != NULL);

  assert(output != NULL && output_size != NULL);

  assert(width > 0 && height > 0);

  assert(pic->a_stride >= width);

  assert(filter >= WEBP_FILTER_NONE && filter <= WEBP_FILTER_FAST);

  if (quality < 0 || quality > 100) {

    return 0;

  }

  if (method < ALPHA_NO_COMPRESSION || method > ALPHA_LOSSLESS_COMPRESSION) {

    return 0;

  }

  if (method == ALPHA_NO_COMPRESSION) {

    // Don't filter, as filtering will make no impact on compressed size.

    filter = WEBP_FILTER_NONE;

  }

  quant_alpha = (uint8_t*)WebPSafeMalloc(1ULL, data_size);

  if (quant_alpha == NULL) {

    return 0;

  }

  // Extract alpha data (width x height) from raw_data (stride x height).

  WebPCopyPlane(pic->a, pic->a_stride, quant_alpha, width, width, height);

  if (reduce_levels) {  // No Quantization required for 'quality = 100'.

    // 16 alpha levels gives quite a low MSE w.r.t original alpha plane hence

    // mapped to moderate quality 70. Hence Quality:[0, 70] -> Levels:[2, 16]

    // and Quality:]70, 100] -> Levels:]16, 256].

    const int alpha_levels = (quality <= 70) ? (2 + quality / 5)

                                             : (16 + (quality - 70) * 8);

    ok = QuantizeLevels(quant_alpha, width, height, alpha_levels, &sse);

  }

  if (ok) {

    VP8FiltersInit();

    ok = ApplyFiltersAndEncode(quant_alpha, width, height, data_size, method,

                               filter, reduce_levels, effort_level, output,

                               output_size, pic->stats);

#if !defined(WEBP_DISABLE_STATS)

    if (pic->stats != NULL) {  // need stats?

      pic->stats->coded_size += (int)(*output_size);

      enc->sse_[3] = sse;

    }

#endif

  }

  WebPSafeFree(quant_alpha);

  return ok;

}

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

// Main calls

static int CompressAlphaJob(void* arg1, void* dummy) {

  VP8Encoder* const enc = (VP8Encoder*)arg1;

  const WebPConfig* config = enc->config_;

  uint8_t* alpha_data = NULL;

  size_t alpha_size = 0;

  const int effort_level = config->method;  // maps to [0..6]

  const WEBP_FILTER_TYPE filter =

      (config->alpha_filtering == 0) ? WEBP_FILTER_NONE :

      (config->alpha_filtering == 1) ? WEBP_FILTER_FAST :

                                       WEBP_FILTER_BEST;

  if (!EncodeAlpha(enc, config->alpha_quality, config->alpha_compression,

                   filter, effort_level, &alpha_data, &alpha_size)) {

    return 0;

  }

  if (alpha_size != (uint32_t)alpha_size) {  // Sanity check.

    WebPSafeFree(alpha_data);

    return 0;

  }

  enc->alpha_data_size_ = (uint32_t)alpha_size;

  enc->alpha_data_ = alpha_data;

  (void)dummy;

  return 1;

}

void VP8EncInitAlpha(VP8Encoder* const enc) {

  WebPInitAlphaProcessing();

  enc->has_alpha_ = WebPPictureHasTransparency(enc->pic_);

  enc->alpha_data_ = NULL;

  enc->alpha_data_size_ = 0;

  if (enc->thread_level_ > 0) {

    WebPWorker* const worker = &enc->alpha_worker_;

    WebPGetWorkerInterface()->Init(worker);

    worker->data1 = enc;

    worker->data2 = NULL;

    worker->hook = CompressAlphaJob;

  }

}

int VP8EncStartAlpha(VP8Encoder* const enc) {

  if (enc->has_alpha_) {

    if (enc->thread_level_ > 0) {

      WebPWorker* const worker = &enc->alpha_worker_;

      // Makes sure worker is good to go.

      if (!WebPGetWorkerInterface()->Reset(worker)) {

        return 0;

      }

      WebPGetWorkerInterface()->Launch(worker);

      return 1;

    } else {

      return CompressAlphaJob(enc, NULL);   // just do the job right away

    }

  }

  return 1;

}

int VP8EncFinishAlpha(VP8Encoder* const enc) {

  if (enc->has_alpha_) {

    if (enc->thread_level_ > 0) {

      WebPWorker* const worker = &enc->alpha_worker_;

      if (!WebPGetWorkerInterface()->Sync(worker)) return 0;  // error

    }

  }

  return WebPReportProgress(enc->pic_, enc->percent_ + 20, &enc->percent_);

}

int VP8EncDeleteAlpha(VP8Encoder* const enc) {

  int ok = 1;

  if (enc->thread_level_ > 0) {

    WebPWorker* const worker = &enc->alpha_worker_;

    // finish anything left in flight

    ok = WebPGetWorkerInterface()->Sync(worker);

    // still need to end the worker, even if !ok

    WebPGetWorkerInterface()->End(worker);

  }

  WebPSafeFree(enc->alpha_data_);

  enc->alpha_data_ = NULL;

  enc->alpha_data_size_ = 0;

  enc->has_alpha_ = 0;

  return ok;

}