diff options
Diffstat (limited to 'src/3rdparty/libwebp/src/enc/histogram.c')
| -rw-r--r-- | src/3rdparty/libwebp/src/enc/histogram.c | 721 |
1 files changed, 475 insertions, 246 deletions
diff --git a/src/3rdparty/libwebp/src/enc/histogram.c b/src/3rdparty/libwebp/src/enc/histogram.c index abd253b..7c6abb4 100644 --- a/src/3rdparty/libwebp/src/enc/histogram.c +++ b/src/3rdparty/libwebp/src/enc/histogram.c @@ -10,31 +10,64 @@ // Author: Jyrki Alakuijala (jyrki@google.com) // #ifdef HAVE_CONFIG_H -#include "config.h" +#include "../webp/config.h" #endif #include <math.h> -#include <stdio.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) { - memset(p->literal_, 0, sizeof(p->literal_)); - memset(p->red_, 0, sizeof(p->red_)); - memset(p->blue_, 0, sizeof(p->blue_)); - memset(p->alpha_, 0, sizeof(p->alpha_)); - memset(p->distance_, 0, sizeof(p->distance_)); - p->bit_cost_ = 0; + 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) { - int i; - for (i = 0; i < refs->size; ++i) { - VP8LHistogramAddSinglePixOrCopy(histo, &refs->refs[i]); + VP8LRefsCursor c = VP8LRefsCursorInit(refs); + while (VP8LRefsCursorOk(&c)) { + VP8LHistogramAddSinglePixOrCopy(histo, c.cur_pos); + VP8LRefsCursorNext(&c); } } @@ -53,13 +86,24 @@ void VP8LHistogramInit(VP8LHistogram* const p, int 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; - VP8LHistogram* bulk; - const uint64_t total_size = sizeof(*set) - + (uint64_t)size * sizeof(*set->histograms) - + (uint64_t)size * sizeof(**set->histograms); + 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; @@ -67,12 +111,15 @@ VP8LHistogramSet* VP8LAllocateHistogramSet(int size, int cache_bits) { memory += sizeof(*set); set->histograms = (VP8LHistogram**)memory; memory += size * sizeof(*set->histograms); - bulk = (VP8LHistogram*)memory; set->max_size = size; set->size = size; for (i = 0; i < size; ++i) { - set->histograms[i] = bulk + 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; } @@ -87,36 +134,21 @@ void VP8LHistogramAddSinglePixOrCopy(VP8LHistogram* const histo, ++histo->literal_[PixOrCopyLiteral(v, 1)]; ++histo->blue_[PixOrCopyLiteral(v, 0)]; } else if (PixOrCopyIsCacheIdx(v)) { - int literal_ix = 256 + NUM_LENGTH_CODES + PixOrCopyCacheIdx(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_[256 + code]; + ++histo->literal_[NUM_LITERAL_CODES + code]; VP8LPrefixEncodeBits(PixOrCopyDistance(v), &code, &extra_bits); ++histo->distance_[code]; } } -static double BitsEntropy(const int* const array, int n) { - double retval = 0.; - int sum = 0; - int nonzeros = 0; - int max_val = 0; - int i; +static WEBP_INLINE double BitsEntropyRefine(int nonzeros, int sum, int max_val, + double retval) { double mix; - 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); - if (nonzeros < 5) { if (nonzeros <= 1) { return 0; @@ -147,95 +179,142 @@ static double BitsEntropy(const int* const array, int n) { } } -// Returns the cost encode the rle-encoded entropy code. -// The constants in this function are experimental. -static double HuffmanCost(const int* const population, int length) { - // 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; - double retval = kHuffmanCodeOfHuffmanCodeSize - kSmallBias; - int streak = 0; - int i = 0; - for (; i < length - 1; ++i) { - ++streak; - if (population[i] == population[i + 1]) { - continue; - } - last_streak_hack: - // population[i] points now to the symbol in the streak of same values. - if (streak > 3) { - if (population[i] == 0) { - retval += 1.5625 + 0.234375 * streak; - } else { - retval += 2.578125 + 0.703125 * streak; - } - } else { - if (population[i] == 0) { - retval += 1.796875 * streak; - } else { - retval += 3.28125 * streak; +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]; } } - streak = 0; } - if (i == length - 1) { - ++streak; - goto last_streak_hack; + 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; } -static double PopulationCost(const int* const population, int length) { +// 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 ExtraCost(const int* const population, int length) { - int i; - double cost = 0.; - for (i = 2; i < length - 2; ++i) cost += (i >> 1) * population[i + 2]; - return cost; +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)) - + PopulationCost(p->red_, 256) - + PopulationCost(p->blue_, 256) - + PopulationCost(p->alpha_, 256) - + PopulationCost(p->distance_, NUM_DISTANCE_CODES) - + ExtraCost(p->literal_ + 256, NUM_LENGTH_CODES) - + ExtraCost(p->distance_, NUM_DISTANCE_CODES); + 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)) - + BitsEntropy(p->red_, 256) - + BitsEntropy(p->blue_, 256) - + BitsEntropy(p->alpha_, 256) - + BitsEntropy(p->distance_, NUM_DISTANCE_CODES) - + ExtraCost(p->literal_ + 256, NUM_LENGTH_CODES) - + ExtraCost(p->distance_, NUM_DISTANCE_CODES); + 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 -// Adds 'in' histogram to 'out' -static void HistogramAdd(const VP8LHistogram* const in, - VP8LHistogram* const out) { - int i; - for (i = 0; i < PIX_OR_COPY_CODES_MAX; ++i) { - out->literal_[i] += in->literal_[i]; - } - for (i = 0; i < NUM_DISTANCE_CODES; ++i) { - out->distance_[i] += in->distance_[i]; - } - for (i = 0; i < 256; ++i) { - out->red_[i] += in->red_[i]; - out->blue_[i] += in->blue_[i]; - out->alpha_[i] += in->alpha_[i]; - } +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 @@ -250,41 +329,14 @@ static double HistogramAddEval(const VP8LHistogram* const a, double cost_threshold) { double cost = 0; const double sum_cost = a->bit_cost_ + b->bit_cost_; - int i; - cost_threshold += sum_cost; - // palette_code_bits_ is part of the cost evaluation for literal_. - // TODO(skal): remove/simplify this palette_code_bits_? - out->palette_code_bits_ = - (a->palette_code_bits_ > b->palette_code_bits_) ? a->palette_code_bits_ : - b->palette_code_bits_; - for (i = 0; i < PIX_OR_COPY_CODES_MAX; ++i) { - out->literal_[i] = a->literal_[i] + b->literal_[i]; - } - cost += PopulationCost(out->literal_, VP8LHistogramNumCodes(out)); - cost += ExtraCost(out->literal_ + 256, NUM_LENGTH_CODES); - if (cost > cost_threshold) return cost; - - for (i = 0; i < 256; ++i) out->red_[i] = a->red_[i] + b->red_[i]; - cost += PopulationCost(out->red_, 256); - if (cost > cost_threshold) return cost; - - for (i = 0; i < 256; ++i) out->blue_[i] = a->blue_[i] + b->blue_[i]; - cost += PopulationCost(out->blue_, 256); - if (cost > cost_threshold) return cost; - - for (i = 0; i < NUM_DISTANCE_CODES; ++i) { - out->distance_[i] = a->distance_[i] + b->distance_[i]; + if (GetCombinedHistogramEntropy(a, b, cost_threshold, &cost)) { + VP8LHistogramAdd(a, b, out); + out->bit_cost_ = cost; + out->palette_code_bits_ = a->palette_code_bits_; } - cost += PopulationCost(out->distance_, NUM_DISTANCE_CODES); - cost += ExtraCost(out->distance_, NUM_DISTANCE_CODES); - if (cost > cost_threshold) return cost; - for (i = 0; i < 256; ++i) out->alpha_[i] = a->alpha_[i] + b->alpha_[i]; - cost += PopulationCost(out->alpha_, 256); - - out->bit_cost_ = cost; return cost - sum_cost; } @@ -294,52 +346,92 @@ static double HistogramAddEval(const VP8LHistogram* const a, static double HistogramAddThresh(const VP8LHistogram* const a, const VP8LHistogram* const b, double cost_threshold) { - int tmp[PIX_OR_COPY_CODES_MAX]; // <= max storage we'll need - int i; double cost = -a->bit_cost_; + GetCombinedHistogramEntropy(a, b, cost_threshold, &cost); + return cost; +} - for (i = 0; i < PIX_OR_COPY_CODES_MAX; ++i) { - tmp[i] = a->literal_[i] + b->literal_[i]; - } - // note that the tests are ordered so that the usually largest - // cost shares come first. - cost += PopulationCost(tmp, VP8LHistogramNumCodes(a)); - cost += ExtraCost(tmp + 256, NUM_LENGTH_CODES); - if (cost > cost_threshold) return cost; - - for (i = 0; i < 256; ++i) tmp[i] = a->red_[i] + b->red_[i]; - cost += PopulationCost(tmp, 256); - if (cost > cost_threshold) return cost; - - for (i = 0; i < 256; ++i) tmp[i] = a->blue_[i] + b->blue_[i]; - cost += PopulationCost(tmp, 256); - if (cost > cost_threshold) return cost; - - for (i = 0; i < NUM_DISTANCE_CODES; ++i) { - tmp[i] = a->distance_[i] + b->distance_[i]; - } - cost += PopulationCost(tmp, NUM_DISTANCE_CODES); - cost += ExtraCost(tmp, NUM_DISTANCE_CODES); - if (cost > cost_threshold) return cost; +// ----------------------------------------------------------------------------- - for (i = 0; i < 256; ++i) tmp[i] = a->alpha_[i] + b->alpha_[i]; - cost += PopulationCost(tmp, 256); +// 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; +} - return 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 void HistogramBuildImage(int xsize, int histo_bits, - const VP8LBackwardRefs* const backward_refs, - VP8LHistogramSet* const image) { - int i; +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->histograms; + VP8LHistogram** const histograms = image_histo->histograms; + VP8LRefsCursor c = VP8LRefsCursorInit(backward_refs); assert(histo_bits > 0); - for (i = 0; i < backward_refs->size; ++i) { - const PixOrCopy* const v = &backward_refs->refs[i]; + // 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); @@ -347,9 +439,119 @@ static void HistogramBuildImage(int xsize, int histo_bits, 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) { @@ -358,48 +560,45 @@ static uint32_t MyRand(uint32_t *seed) { return *seed; } -static int HistogramCombine(const VP8LHistogramSet* const in, - VP8LHistogramSet* const out, int iter_mult, - int num_pairs, int num_tries_no_success) { - int ok = 0; - int i, iter; +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 out_size = in->size; - const int outer_iters = in->size * iter_mult; + 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 histos = (VP8LHistogram*)malloc(2 * sizeof(*histos)); - VP8LHistogram* cur_combo = histos + 0; // trial merged histogram - VP8LHistogram* best_combo = histos + 1; // best merged histogram so far - if (histos == NULL) goto End; - - // Copy histograms from in[] to out[]. - assert(in->size <= out->size); - for (i = 0; i < in->size; ++i) { - in->histograms[i]->bit_cost_ = VP8LHistogramEstimateBits(in->histograms[i]); - *out->histograms[i] = *in->histograms[i]; - } - - // Collapse similar histograms in 'out'. - for (iter = 0; iter < outer_iters && out_size >= min_cluster_size; ++iter) { + 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 < out_size) ? num_pairs : out_size; + 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) % out_size; + 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) % (out_size - 1); - const uint32_t idx2 = (idx1 + diff + 1) % out_size; + 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(out->histograms[idx1], - out->histograms[idx2], + 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 @@ -414,12 +613,12 @@ static int HistogramCombine(const VP8LHistogramSet* const in, } if (best_idx1 >= 0) { - *out->histograms[best_idx1] = *best_combo; + HistogramCopy(best_combo, histograms[best_idx1]); // swap best_idx2 slot with last one (which is now unused) - --out_size; - if (best_idx2 != out_size) { - out->histograms[best_idx2] = out->histograms[out_size]; - out->histograms[out_size] = NULL; // just for sanity check. + --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; } @@ -427,38 +626,28 @@ static int HistogramCombine(const VP8LHistogramSet* const in, break; } } - out->size = out_size; - ok = 1; - - End: - free(histos); - return ok; + image_histo->size = image_histo_size; } // ----------------------------------------------------------------------------- // Histogram refinement -// What is the bit cost of moving square_histogram from cur_symbol to candidate. -static double HistogramDistance(const VP8LHistogram* const square_histogram, - const VP8LHistogram* const candidate, - double cost_threshold) { - return HistogramAddThresh(candidate, square_histogram, cost_threshold); -} - // 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 in, - const VP8LHistogramSet* const out, +static void HistogramRemap(const VP8LHistogramSet* const orig_histo, + const VP8LHistogramSet* const image_histo, uint16_t* const symbols) { int i; - for (i = 0; i < in->size; ++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 = - HistogramDistance(in->histograms[i], out->histograms[0], 1.e38); + HistogramAddThresh(histograms[0], orig_histograms[i], MAX_COST); int k; - for (k = 1; k < out->size; ++k) { + for (k = 1; k < image_histo->size; ++k) { const double cur_bits = - HistogramDistance(in->histograms[i], out->histograms[k], best_bits); + HistogramAddThresh(histograms[k], orig_histograms[i], best_bits); if (cur_bits < best_bits) { best_bits = cur_bits; best_out = k; @@ -468,45 +657,85 @@ static void HistogramRemap(const VP8LHistogramSet* const in, } // Recompute each out based on raw and symbols. - for (i = 0; i < out->size; ++i) { - HistogramClear(out->histograms[i]); + for (i = 0; i < image_histo->size; ++i) { + HistogramClear(histograms[i]); } - for (i = 0; i < in->size; ++i) { - HistogramAdd(in->histograms[i], out->histograms[symbols[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_in, + 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 histo_image_raw_size = histo_xsize * histo_ysize; - - // Heuristic params for HistogramCombine(). - const int num_tries_no_success = 8 + (quality >> 1); - const int iter_mult = (quality < 27) ? 1 : 1 + ((quality - 27) >> 4); - const int num_pairs = (quality < 25) ? 10 : (5 * quality) >> 3; - - VP8LHistogramSet* const image_out = - VP8LAllocateHistogramSet(histo_image_raw_size, cache_bits); - if (image_out == NULL) return 0; - - // Build histogram image. - HistogramBuildImage(xsize, histo_bits, refs, image_out); - // Collapse similar histograms. - if (!HistogramCombine(image_out, image_in, iter_mult, num_pairs, - num_tries_no_success)) { + 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(image_out, image_in, histogram_symbols); + HistogramRemap(orig_histo, image_histo, histogram_symbols); + ok = 1; -Error: - free(image_out); + Error: + WebPSafeFree(bin_map); + VP8LFreeHistogramSet(orig_histo); + VP8LFreeHistogramSet(histos); return ok; } |