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- // Copyright 2012 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.
- // -----------------------------------------------------------------------------
- //
- // Author: Jyrki Alakuijala (jyrki@google.com)
- //
- #ifdef HAVE_CONFIG_H
- #include "../webp/config.h"
- #endif
- #include <math.h>
- #include "./backward_references.h"
- #include "./histogram.h"
- #include "../dsp/lossless.h"
- #include "../utils/utils.h"
- #define MAX_COST 1.e38
- // Number of partitions for the three dominant (literal, red and blue) symbol
- // costs.
- #define NUM_PARTITIONS 4
- // The size of the bin-hash corresponding to the three dominant costs.
- #define BIN_SIZE (NUM_PARTITIONS * NUM_PARTITIONS * NUM_PARTITIONS)
- static void HistogramClear(VP8LHistogram* const p) {
- uint32_t* const literal = p->literal_;
- const int cache_bits = p->palette_code_bits_;
- const int histo_size = VP8LGetHistogramSize(cache_bits);
- memset(p, 0, histo_size);
- p->palette_code_bits_ = cache_bits;
- p->literal_ = literal;
- }
- static void HistogramCopy(const VP8LHistogram* const src,
- VP8LHistogram* const dst) {
- uint32_t* const dst_literal = dst->literal_;
- const int dst_cache_bits = dst->palette_code_bits_;
- const int histo_size = VP8LGetHistogramSize(dst_cache_bits);
- assert(src->palette_code_bits_ == dst_cache_bits);
- memcpy(dst, src, histo_size);
- dst->literal_ = dst_literal;
- }
- int VP8LGetHistogramSize(int cache_bits) {
- const int literal_size = VP8LHistogramNumCodes(cache_bits);
- const size_t total_size = sizeof(VP8LHistogram) + sizeof(int) * literal_size;
- assert(total_size <= (size_t)0x7fffffff);
- return (int)total_size;
- }
- void VP8LFreeHistogram(VP8LHistogram* const histo) {
- WebPSafeFree(histo);
- }
- void VP8LFreeHistogramSet(VP8LHistogramSet* const histo) {
- WebPSafeFree(histo);
- }
- void VP8LHistogramStoreRefs(const VP8LBackwardRefs* const refs,
- VP8LHistogram* const histo) {
- VP8LRefsCursor c = VP8LRefsCursorInit(refs);
- while (VP8LRefsCursorOk(&c)) {
- VP8LHistogramAddSinglePixOrCopy(histo, c.cur_pos);
- VP8LRefsCursorNext(&c);
- }
- }
- void VP8LHistogramCreate(VP8LHistogram* const p,
- const VP8LBackwardRefs* const refs,
- int palette_code_bits) {
- if (palette_code_bits >= 0) {
- p->palette_code_bits_ = palette_code_bits;
- }
- HistogramClear(p);
- VP8LHistogramStoreRefs(refs, p);
- }
- void VP8LHistogramInit(VP8LHistogram* const p, int palette_code_bits) {
- p->palette_code_bits_ = palette_code_bits;
- HistogramClear(p);
- }
- VP8LHistogram* VP8LAllocateHistogram(int cache_bits) {
- VP8LHistogram* histo = NULL;
- const int total_size = VP8LGetHistogramSize(cache_bits);
- uint8_t* const memory = (uint8_t*)WebPSafeMalloc(total_size, sizeof(*memory));
- if (memory == NULL) return NULL;
- histo = (VP8LHistogram*)memory;
- // literal_ won't necessary be aligned.
- histo->literal_ = (uint32_t*)(memory + sizeof(VP8LHistogram));
- VP8LHistogramInit(histo, cache_bits);
- return histo;
- }
- VP8LHistogramSet* VP8LAllocateHistogramSet(int size, int cache_bits) {
- int i;
- VP8LHistogramSet* set;
- const size_t total_size = sizeof(*set)
- + sizeof(*set->histograms) * size
- + (size_t)VP8LGetHistogramSize(cache_bits) * size;
- uint8_t* memory = (uint8_t*)WebPSafeMalloc(total_size, sizeof(*memory));
- if (memory == NULL) return NULL;
- set = (VP8LHistogramSet*)memory;
- memory += sizeof(*set);
- set->histograms = (VP8LHistogram**)memory;
- memory += size * sizeof(*set->histograms);
- set->max_size = size;
- set->size = size;
- for (i = 0; i < size; ++i) {
- set->histograms[i] = (VP8LHistogram*)memory;
- // literal_ won't necessary be aligned.
- set->histograms[i]->literal_ = (uint32_t*)(memory + sizeof(VP8LHistogram));
- VP8LHistogramInit(set->histograms[i], cache_bits);
- // There's no padding/alignment between successive histograms.
- memory += VP8LGetHistogramSize(cache_bits);
- }
- return set;
- }
- // -----------------------------------------------------------------------------
- void VP8LHistogramAddSinglePixOrCopy(VP8LHistogram* const histo,
- const PixOrCopy* const v) {
- if (PixOrCopyIsLiteral(v)) {
- ++histo->alpha_[PixOrCopyLiteral(v, 3)];
- ++histo->red_[PixOrCopyLiteral(v, 2)];
- ++histo->literal_[PixOrCopyLiteral(v, 1)];
- ++histo->blue_[PixOrCopyLiteral(v, 0)];
- } else if (PixOrCopyIsCacheIdx(v)) {
- const int literal_ix =
- NUM_LITERAL_CODES + NUM_LENGTH_CODES + PixOrCopyCacheIdx(v);
- ++histo->literal_[literal_ix];
- } else {
- int code, extra_bits;
- VP8LPrefixEncodeBits(PixOrCopyLength(v), &code, &extra_bits);
- ++histo->literal_[NUM_LITERAL_CODES + code];
- VP8LPrefixEncodeBits(PixOrCopyDistance(v), &code, &extra_bits);
- ++histo->distance_[code];
- }
- }
- static WEBP_INLINE double BitsEntropyRefine(int nonzeros, int sum, int max_val,
- double retval) {
- double mix;
- if (nonzeros < 5) {
- if (nonzeros <= 1) {
- return 0;
- }
- // Two symbols, they will be 0 and 1 in a Huffman code.
- // Let's mix in a bit of entropy to favor good clustering when
- // distributions of these are combined.
- if (nonzeros == 2) {
- return 0.99 * sum + 0.01 * retval;
- }
- // No matter what the entropy says, we cannot be better than min_limit
- // with Huffman coding. I am mixing a bit of entropy into the
- // min_limit since it produces much better (~0.5 %) compression results
- // perhaps because of better entropy clustering.
- if (nonzeros == 3) {
- mix = 0.95;
- } else {
- mix = 0.7; // nonzeros == 4.
- }
- } else {
- mix = 0.627;
- }
- {
- double min_limit = 2 * sum - max_val;
- min_limit = mix * min_limit + (1.0 - mix) * retval;
- return (retval < min_limit) ? min_limit : retval;
- }
- }
- static double BitsEntropy(const uint32_t* const array, int n) {
- double retval = 0.;
- uint32_t sum = 0;
- int nonzeros = 0;
- uint32_t max_val = 0;
- int i;
- for (i = 0; i < n; ++i) {
- if (array[i] != 0) {
- sum += array[i];
- ++nonzeros;
- retval -= VP8LFastSLog2(array[i]);
- if (max_val < array[i]) {
- max_val = array[i];
- }
- }
- }
- retval += VP8LFastSLog2(sum);
- return BitsEntropyRefine(nonzeros, sum, max_val, retval);
- }
- static double BitsEntropyCombined(const uint32_t* const X,
- const uint32_t* const Y, int n) {
- double retval = 0.;
- int sum = 0;
- int nonzeros = 0;
- int max_val = 0;
- int i;
- for (i = 0; i < n; ++i) {
- const int xy = X[i] + Y[i];
- if (xy != 0) {
- sum += xy;
- ++nonzeros;
- retval -= VP8LFastSLog2(xy);
- if (max_val < xy) {
- max_val = xy;
- }
- }
- }
- retval += VP8LFastSLog2(sum);
- return BitsEntropyRefine(nonzeros, sum, max_val, retval);
- }
- static double InitialHuffmanCost(void) {
- // Small bias because Huffman code length is typically not stored in
- // full length.
- static const int kHuffmanCodeOfHuffmanCodeSize = CODE_LENGTH_CODES * 3;
- static const double kSmallBias = 9.1;
- return kHuffmanCodeOfHuffmanCodeSize - kSmallBias;
- }
- // Finalize the Huffman cost based on streak numbers and length type (<3 or >=3)
- static double FinalHuffmanCost(const VP8LStreaks* const stats) {
- double retval = InitialHuffmanCost();
- retval += stats->counts[0] * 1.5625 + 0.234375 * stats->streaks[0][1];
- retval += stats->counts[1] * 2.578125 + 0.703125 * stats->streaks[1][1];
- retval += 1.796875 * stats->streaks[0][0];
- retval += 3.28125 * stats->streaks[1][0];
- return retval;
- }
- // Trampolines
- static double HuffmanCost(const uint32_t* const population, int length) {
- const VP8LStreaks stats = VP8LHuffmanCostCount(population, length);
- return FinalHuffmanCost(&stats);
- }
- static double HuffmanCostCombined(const uint32_t* const X,
- const uint32_t* const Y, int length) {
- const VP8LStreaks stats = VP8LHuffmanCostCombinedCount(X, Y, length);
- return FinalHuffmanCost(&stats);
- }
- // Aggregated costs
- static double PopulationCost(const uint32_t* const population, int length) {
- return BitsEntropy(population, length) + HuffmanCost(population, length);
- }
- static double GetCombinedEntropy(const uint32_t* const X,
- const uint32_t* const Y, int length) {
- return BitsEntropyCombined(X, Y, length) + HuffmanCostCombined(X, Y, length);
- }
- // Estimates the Entropy + Huffman + other block overhead size cost.
- double VP8LHistogramEstimateBits(const VP8LHistogram* const p) {
- return
- PopulationCost(p->literal_, VP8LHistogramNumCodes(p->palette_code_bits_))
- + PopulationCost(p->red_, NUM_LITERAL_CODES)
- + PopulationCost(p->blue_, NUM_LITERAL_CODES)
- + PopulationCost(p->alpha_, NUM_LITERAL_CODES)
- + PopulationCost(p->distance_, NUM_DISTANCE_CODES)
- + VP8LExtraCost(p->literal_ + NUM_LITERAL_CODES, NUM_LENGTH_CODES)
- + VP8LExtraCost(p->distance_, NUM_DISTANCE_CODES);
- }
- double VP8LHistogramEstimateBitsBulk(const VP8LHistogram* const p) {
- return
- BitsEntropy(p->literal_, VP8LHistogramNumCodes(p->palette_code_bits_))
- + BitsEntropy(p->red_, NUM_LITERAL_CODES)
- + BitsEntropy(p->blue_, NUM_LITERAL_CODES)
- + BitsEntropy(p->alpha_, NUM_LITERAL_CODES)
- + BitsEntropy(p->distance_, NUM_DISTANCE_CODES)
- + VP8LExtraCost(p->literal_ + NUM_LITERAL_CODES, NUM_LENGTH_CODES)
- + VP8LExtraCost(p->distance_, NUM_DISTANCE_CODES);
- }
- // -----------------------------------------------------------------------------
- // Various histogram combine/cost-eval functions
- static int GetCombinedHistogramEntropy(const VP8LHistogram* const a,
- const VP8LHistogram* const b,
- double cost_threshold,
- double* cost) {
- const int palette_code_bits = a->palette_code_bits_;
- assert(a->palette_code_bits_ == b->palette_code_bits_);
- *cost += GetCombinedEntropy(a->literal_, b->literal_,
- VP8LHistogramNumCodes(palette_code_bits));
- *cost += VP8LExtraCostCombined(a->literal_ + NUM_LITERAL_CODES,
- b->literal_ + NUM_LITERAL_CODES,
- NUM_LENGTH_CODES);
- if (*cost > cost_threshold) return 0;
- *cost += GetCombinedEntropy(a->red_, b->red_, NUM_LITERAL_CODES);
- if (*cost > cost_threshold) return 0;
- *cost += GetCombinedEntropy(a->blue_, b->blue_, NUM_LITERAL_CODES);
- if (*cost > cost_threshold) return 0;
- *cost += GetCombinedEntropy(a->alpha_, b->alpha_, NUM_LITERAL_CODES);
- if (*cost > cost_threshold) return 0;
- *cost += GetCombinedEntropy(a->distance_, b->distance_, NUM_DISTANCE_CODES);
- *cost += VP8LExtraCostCombined(a->distance_, b->distance_,
- NUM_DISTANCE_CODES);
- if (*cost > cost_threshold) return 0;
- return 1;
- }
- // Performs out = a + b, computing the cost C(a+b) - C(a) - C(b) while comparing
- // to the threshold value 'cost_threshold'. The score returned is
- // Score = C(a+b) - C(a) - C(b), where C(a) + C(b) is known and fixed.
- // Since the previous score passed is 'cost_threshold', we only need to compare
- // the partial cost against 'cost_threshold + C(a) + C(b)' to possibly bail-out
- // early.
- static double HistogramAddEval(const VP8LHistogram* const a,
- const VP8LHistogram* const b,
- VP8LHistogram* const out,
- double cost_threshold) {
- double cost = 0;
- const double sum_cost = a->bit_cost_ + b->bit_cost_;
- cost_threshold += sum_cost;
- if (GetCombinedHistogramEntropy(a, b, cost_threshold, &cost)) {
- VP8LHistogramAdd(a, b, out);
- out->bit_cost_ = cost;
- out->palette_code_bits_ = a->palette_code_bits_;
- }
- return cost - sum_cost;
- }
- // Same as HistogramAddEval(), except that the resulting histogram
- // is not stored. Only the cost C(a+b) - C(a) is evaluated. We omit
- // the term C(b) which is constant over all the evaluations.
- static double HistogramAddThresh(const VP8LHistogram* const a,
- const VP8LHistogram* const b,
- double cost_threshold) {
- double cost = -a->bit_cost_;
- GetCombinedHistogramEntropy(a, b, cost_threshold, &cost);
- return cost;
- }
- // -----------------------------------------------------------------------------
- // The structure to keep track of cost range for the three dominant entropy
- // symbols.
- // TODO(skal): Evaluate if float can be used here instead of double for
- // representing the entropy costs.
- typedef struct {
- double literal_max_;
- double literal_min_;
- double red_max_;
- double red_min_;
- double blue_max_;
- double blue_min_;
- } DominantCostRange;
- static void DominantCostRangeInit(DominantCostRange* const c) {
- c->literal_max_ = 0.;
- c->literal_min_ = MAX_COST;
- c->red_max_ = 0.;
- c->red_min_ = MAX_COST;
- c->blue_max_ = 0.;
- c->blue_min_ = MAX_COST;
- }
- static void UpdateDominantCostRange(
- const VP8LHistogram* const h, DominantCostRange* const c) {
- if (c->literal_max_ < h->literal_cost_) c->literal_max_ = h->literal_cost_;
- if (c->literal_min_ > h->literal_cost_) c->literal_min_ = h->literal_cost_;
- if (c->red_max_ < h->red_cost_) c->red_max_ = h->red_cost_;
- if (c->red_min_ > h->red_cost_) c->red_min_ = h->red_cost_;
- if (c->blue_max_ < h->blue_cost_) c->blue_max_ = h->blue_cost_;
- if (c->blue_min_ > h->blue_cost_) c->blue_min_ = h->blue_cost_;
- }
- static void UpdateHistogramCost(VP8LHistogram* const h) {
- const double alpha_cost = PopulationCost(h->alpha_, NUM_LITERAL_CODES);
- const double distance_cost =
- PopulationCost(h->distance_, NUM_DISTANCE_CODES) +
- VP8LExtraCost(h->distance_, NUM_DISTANCE_CODES);
- const int num_codes = VP8LHistogramNumCodes(h->palette_code_bits_);
- h->literal_cost_ = PopulationCost(h->literal_, num_codes) +
- VP8LExtraCost(h->literal_ + NUM_LITERAL_CODES,
- NUM_LENGTH_CODES);
- h->red_cost_ = PopulationCost(h->red_, NUM_LITERAL_CODES);
- h->blue_cost_ = PopulationCost(h->blue_, NUM_LITERAL_CODES);
- h->bit_cost_ = h->literal_cost_ + h->red_cost_ + h->blue_cost_ +
- alpha_cost + distance_cost;
- }
- static int GetBinIdForEntropy(double min, double max, double val) {
- const double range = max - min + 1e-6;
- const double delta = val - min;
- return (int)(NUM_PARTITIONS * delta / range);
- }
- // TODO(vikasa): Evaluate, if there's any correlation between red & blue.
- static int GetHistoBinIndex(
- const VP8LHistogram* const h, const DominantCostRange* const c) {
- const int bin_id =
- GetBinIdForEntropy(c->blue_min_, c->blue_max_, h->blue_cost_) +
- NUM_PARTITIONS * GetBinIdForEntropy(c->red_min_, c->red_max_,
- h->red_cost_) +
- NUM_PARTITIONS * NUM_PARTITIONS * GetBinIdForEntropy(c->literal_min_,
- c->literal_max_,
- h->literal_cost_);
- assert(bin_id < BIN_SIZE);
- return bin_id;
- }
- // Construct the histograms from backward references.
- static void HistogramBuild(
- int xsize, int histo_bits, const VP8LBackwardRefs* const backward_refs,
- VP8LHistogramSet* const image_histo) {
- int x = 0, y = 0;
- const int histo_xsize = VP8LSubSampleSize(xsize, histo_bits);
- VP8LHistogram** const histograms = image_histo->histograms;
- VP8LRefsCursor c = VP8LRefsCursorInit(backward_refs);
- assert(histo_bits > 0);
- // Construct the Histo from a given backward references.
- while (VP8LRefsCursorOk(&c)) {
- const PixOrCopy* const v = c.cur_pos;
- const int ix = (y >> histo_bits) * histo_xsize + (x >> histo_bits);
- VP8LHistogramAddSinglePixOrCopy(histograms[ix], v);
- x += PixOrCopyLength(v);
- while (x >= xsize) {
- x -= xsize;
- ++y;
- }
- VP8LRefsCursorNext(&c);
- }
- }
- // Copies the histograms and computes its bit_cost.
- static void HistogramCopyAndAnalyze(
- VP8LHistogramSet* const orig_histo, VP8LHistogramSet* const image_histo) {
- int i;
- const int histo_size = orig_histo->size;
- VP8LHistogram** const orig_histograms = orig_histo->histograms;
- VP8LHistogram** const histograms = image_histo->histograms;
- for (i = 0; i < histo_size; ++i) {
- VP8LHistogram* const histo = orig_histograms[i];
- UpdateHistogramCost(histo);
- // Copy histograms from orig_histo[] to image_histo[].
- HistogramCopy(histo, histograms[i]);
- }
- }
- // Partition histograms to different entropy bins for three dominant (literal,
- // red and blue) symbol costs and compute the histogram aggregate bit_cost.
- static void HistogramAnalyzeEntropyBin(
- VP8LHistogramSet* const image_histo, int16_t* const bin_map) {
- int i;
- VP8LHistogram** const histograms = image_histo->histograms;
- const int histo_size = image_histo->size;
- const int bin_depth = histo_size + 1;
- DominantCostRange cost_range;
- DominantCostRangeInit(&cost_range);
- // Analyze the dominant (literal, red and blue) entropy costs.
- for (i = 0; i < histo_size; ++i) {
- VP8LHistogram* const histo = histograms[i];
- UpdateDominantCostRange(histo, &cost_range);
- }
- // bin-hash histograms on three of the dominant (literal, red and blue)
- // symbol costs.
- for (i = 0; i < histo_size; ++i) {
- int num_histos;
- VP8LHistogram* const histo = histograms[i];
- const int16_t bin_id = (int16_t)GetHistoBinIndex(histo, &cost_range);
- const int bin_offset = bin_id * bin_depth;
- // bin_map[n][0] for every bin 'n' maintains the counter for the number of
- // histograms in that bin.
- // Get and increment the num_histos in that bin.
- num_histos = ++bin_map[bin_offset];
- assert(bin_offset + num_histos < bin_depth * BIN_SIZE);
- // Add histogram i'th index at num_histos (last) position in the bin_map.
- bin_map[bin_offset + num_histos] = i;
- }
- }
- // Compact the histogram set by moving the valid one left in the set to the
- // head and moving the ones that have been merged to other histograms towards
- // the end.
- // TODO(vikasa): Evaluate if this method can be avoided by altering the code
- // logic of HistogramCombineEntropyBin main loop.
- static void HistogramCompactBins(VP8LHistogramSet* const image_histo) {
- int start = 0;
- int end = image_histo->size - 1;
- VP8LHistogram** const histograms = image_histo->histograms;
- while (start < end) {
- while (start <= end && histograms[start] != NULL &&
- histograms[start]->bit_cost_ != 0.) {
- ++start;
- }
- while (start <= end && histograms[end]->bit_cost_ == 0.) {
- histograms[end] = NULL;
- --end;
- }
- if (start < end) {
- assert(histograms[start] != NULL);
- assert(histograms[end] != NULL);
- HistogramCopy(histograms[end], histograms[start]);
- histograms[end] = NULL;
- --end;
- }
- }
- image_histo->size = end + 1;
- }
- static void HistogramCombineEntropyBin(VP8LHistogramSet* const image_histo,
- VP8LHistogram* const histos,
- int16_t* const bin_map, int bin_depth,
- double combine_cost_factor) {
- int bin_id;
- VP8LHistogram* cur_combo = histos;
- VP8LHistogram** const histograms = image_histo->histograms;
- for (bin_id = 0; bin_id < BIN_SIZE; ++bin_id) {
- const int bin_offset = bin_id * bin_depth;
- const int num_histos = bin_map[bin_offset];
- const int idx1 = bin_map[bin_offset + 1];
- int n;
- for (n = 2; n <= num_histos; ++n) {
- const int idx2 = bin_map[bin_offset + n];
- const double bit_cost_idx2 = histograms[idx2]->bit_cost_;
- if (bit_cost_idx2 > 0.) {
- const double bit_cost_thresh = -bit_cost_idx2 * combine_cost_factor;
- const double curr_cost_diff =
- HistogramAddEval(histograms[idx1], histograms[idx2],
- cur_combo, bit_cost_thresh);
- if (curr_cost_diff < bit_cost_thresh) {
- HistogramCopy(cur_combo, histograms[idx1]);
- histograms[idx2]->bit_cost_ = 0.;
- }
- }
- }
- }
- HistogramCompactBins(image_histo);
- }
- static uint32_t MyRand(uint32_t *seed) {
- *seed *= 16807U;
- if (*seed == 0) {
- *seed = 1;
- }
- return *seed;
- }
- static void HistogramCombine(VP8LHistogramSet* const image_histo,
- VP8LHistogramSet* const histos, int quality) {
- int iter;
- uint32_t seed = 0;
- int tries_with_no_success = 0;
- int image_histo_size = image_histo->size;
- const int iter_mult = (quality < 25) ? 2 : 2 + (quality - 25) / 8;
- const int outer_iters = image_histo_size * iter_mult;
- const int num_pairs = image_histo_size / 2;
- const int num_tries_no_success = outer_iters / 2;
- const int min_cluster_size = 2;
- VP8LHistogram** const histograms = image_histo->histograms;
- VP8LHistogram* cur_combo = histos->histograms[0]; // trial histogram
- VP8LHistogram* best_combo = histos->histograms[1]; // best histogram so far
- // Collapse similar histograms in 'image_histo'.
- for (iter = 0;
- iter < outer_iters && image_histo_size >= min_cluster_size;
- ++iter) {
- double best_cost_diff = 0.;
- int best_idx1 = -1, best_idx2 = 1;
- int j;
- const int num_tries =
- (num_pairs < image_histo_size) ? num_pairs : image_histo_size;
- seed += iter;
- for (j = 0; j < num_tries; ++j) {
- double curr_cost_diff;
- // Choose two histograms at random and try to combine them.
- const uint32_t idx1 = MyRand(&seed) % image_histo_size;
- const uint32_t tmp = (j & 7) + 1;
- const uint32_t diff =
- (tmp < 3) ? tmp : MyRand(&seed) % (image_histo_size - 1);
- const uint32_t idx2 = (idx1 + diff + 1) % image_histo_size;
- if (idx1 == idx2) {
- continue;
- }
- // Calculate cost reduction on combining.
- curr_cost_diff = HistogramAddEval(histograms[idx1], histograms[idx2],
- cur_combo, best_cost_diff);
- if (curr_cost_diff < best_cost_diff) { // found a better pair?
- { // swap cur/best combo histograms
- VP8LHistogram* const tmp_histo = cur_combo;
- cur_combo = best_combo;
- best_combo = tmp_histo;
- }
- best_cost_diff = curr_cost_diff;
- best_idx1 = idx1;
- best_idx2 = idx2;
- }
- }
- if (best_idx1 >= 0) {
- HistogramCopy(best_combo, histograms[best_idx1]);
- // swap best_idx2 slot with last one (which is now unused)
- --image_histo_size;
- if (best_idx2 != image_histo_size) {
- HistogramCopy(histograms[image_histo_size], histograms[best_idx2]);
- histograms[image_histo_size] = NULL;
- }
- tries_with_no_success = 0;
- }
- if (++tries_with_no_success >= num_tries_no_success) {
- break;
- }
- }
- image_histo->size = image_histo_size;
- }
- // -----------------------------------------------------------------------------
- // Histogram refinement
- // Find the best 'out' histogram for each of the 'in' histograms.
- // Note: we assume that out[]->bit_cost_ is already up-to-date.
- static void HistogramRemap(const VP8LHistogramSet* const orig_histo,
- const VP8LHistogramSet* const image_histo,
- uint16_t* const symbols) {
- int i;
- VP8LHistogram** const orig_histograms = orig_histo->histograms;
- VP8LHistogram** const histograms = image_histo->histograms;
- for (i = 0; i < orig_histo->size; ++i) {
- int best_out = 0;
- double best_bits =
- HistogramAddThresh(histograms[0], orig_histograms[i], MAX_COST);
- int k;
- for (k = 1; k < image_histo->size; ++k) {
- const double cur_bits =
- HistogramAddThresh(histograms[k], orig_histograms[i], best_bits);
- if (cur_bits < best_bits) {
- best_bits = cur_bits;
- best_out = k;
- }
- }
- symbols[i] = best_out;
- }
- // Recompute each out based on raw and symbols.
- for (i = 0; i < image_histo->size; ++i) {
- HistogramClear(histograms[i]);
- }
- for (i = 0; i < orig_histo->size; ++i) {
- const int idx = symbols[i];
- VP8LHistogramAdd(orig_histograms[i], histograms[idx], histograms[idx]);
- }
- }
- static double GetCombineCostFactor(int histo_size, int quality) {
- double combine_cost_factor = 0.16;
- if (histo_size > 256) combine_cost_factor /= 2.;
- if (histo_size > 512) combine_cost_factor /= 2.;
- if (histo_size > 1024) combine_cost_factor /= 2.;
- if (quality <= 50) combine_cost_factor /= 2.;
- return combine_cost_factor;
- }
- int VP8LGetHistoImageSymbols(int xsize, int ysize,
- const VP8LBackwardRefs* const refs,
- int quality, int histo_bits, int cache_bits,
- VP8LHistogramSet* const image_histo,
- uint16_t* const histogram_symbols) {
- int ok = 0;
- const int histo_xsize = histo_bits ? VP8LSubSampleSize(xsize, histo_bits) : 1;
- const int histo_ysize = histo_bits ? VP8LSubSampleSize(ysize, histo_bits) : 1;
- const int image_histo_raw_size = histo_xsize * histo_ysize;
- // The bin_map for every bin follows following semantics:
- // bin_map[n][0] = num_histo; // The number of histograms in that bin.
- // bin_map[n][1] = index of first histogram in that bin;
- // bin_map[n][num_histo] = index of last histogram in that bin;
- // bin_map[n][num_histo + 1] ... bin_map[n][bin_depth - 1] = un-used indices.
- const int bin_depth = image_histo_raw_size + 1;
- int16_t* bin_map = NULL;
- VP8LHistogramSet* const histos = VP8LAllocateHistogramSet(2, cache_bits);
- VP8LHistogramSet* const orig_histo =
- VP8LAllocateHistogramSet(image_histo_raw_size, cache_bits);
- if (orig_histo == NULL || histos == NULL) {
- goto Error;
- }
- // Don't attempt linear bin-partition heuristic for:
- // histograms of small sizes, as bin_map will be very sparse and;
- // Higher qualities (> 90), to preserve the compression gains at those
- // quality settings.
- if (orig_histo->size > 2 * BIN_SIZE && quality < 90) {
- const int bin_map_size = bin_depth * BIN_SIZE;
- bin_map = (int16_t*)WebPSafeCalloc(bin_map_size, sizeof(*bin_map));
- if (bin_map == NULL) goto Error;
- }
- // Construct the histograms from backward references.
- HistogramBuild(xsize, histo_bits, refs, orig_histo);
- // Copies the histograms and computes its bit_cost.
- HistogramCopyAndAnalyze(orig_histo, image_histo);
- if (bin_map != NULL) {
- const double combine_cost_factor =
- GetCombineCostFactor(image_histo_raw_size, quality);
- HistogramAnalyzeEntropyBin(orig_histo, bin_map);
- // Collapse histograms with similar entropy.
- HistogramCombineEntropyBin(image_histo, histos->histograms[0],
- bin_map, bin_depth, combine_cost_factor);
- }
- // Collapse similar histograms by random histogram-pair compares.
- HistogramCombine(image_histo, histos, quality);
- // Find the optimal map from original histograms to the final ones.
- HistogramRemap(orig_histo, image_histo, histogram_symbols);
- ok = 1;
- Error:
- WebPSafeFree(bin_map);
- VP8LFreeHistogramSet(orig_histo);
- VP8LFreeHistogramSet(histos);
- return ok;
- }
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