diff options
Diffstat (limited to 'drivers/webp/enc/histogram.c')
| -rw-r--r-- | drivers/webp/enc/histogram.c | 980 |
1 files changed, 736 insertions, 244 deletions
diff --git a/drivers/webp/enc/histogram.c b/drivers/webp/enc/histogram.c index ca838e064d..68c27fb1db 100644 --- a/drivers/webp/enc/histogram.c +++ b/drivers/webp/enc/histogram.c @@ -1,38 +1,82 @@ // Copyright 2012 Google Inc. All Rights Reserved. // -// This code is licensed under the same terms as WebM: -// Software License Agreement: http://www.webmproject.org/license/software/ -// Additional IP Rights Grant: http://www.webmproject.org/license/additional/ +// 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 "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) +// Maximum number of histograms allowed in greedy combining algorithm. +#define MAX_HISTO_GREEDY 100 + 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; +} + +// Swap two histogram pointers. +static void HistogramSwap(VP8LHistogram** const A, VP8LHistogram** const B) { + VP8LHistogram* const tmp = *A; + *A = *B; + *B = tmp; +} + +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); } } @@ -51,13 +95,25 @@ 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 = (uint64_t)sizeof(*set) - + size * sizeof(*set->histograms) - + size * sizeof(**set->histograms); + const int histo_size = VP8LGetHistogramSize(cache_bits); + const size_t total_size = + sizeof(*set) + size * (sizeof(*set->histograms) + + histo_size + WEBP_ALIGN_CST); uint8_t* memory = (uint8_t*)WebPSafeMalloc(total_size, sizeof(*memory)); if (memory == NULL) return NULL; @@ -65,12 +121,15 @@ 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; + memory = (uint8_t*)WEBP_ALIGN(memory); + 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); + memory += histo_size; } return set; } @@ -85,151 +144,183 @@ 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_count, extra_bits_value; - PrefixEncode(PixOrCopyLength(v), - &code, &extra_bits_count, &extra_bits_value); - ++histo->literal_[256 + code]; - PrefixEncode(PixOrCopyDistance(v), - &code, &extra_bits_count, &extra_bits_value); + 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]; } } +// ----------------------------------------------------------------------------- +// 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 += VP8LGetCombinedEntropy(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 += VP8LGetCombinedEntropy(a->red_, b->red_, NUM_LITERAL_CODES); + if (*cost > cost_threshold) return 0; + + *cost += VP8LGetCombinedEntropy(a->blue_, b->blue_, NUM_LITERAL_CODES); + if (*cost > cost_threshold) return 0; + + *cost += VP8LGetCombinedEntropy(a->alpha_, b->alpha_, NUM_LITERAL_CODES); + if (*cost > cost_threshold) return 0; + + *cost += VP8LGetCombinedEntropy(a->distance_, b->distance_, + NUM_DISTANCE_CODES); + *cost += VP8LExtraCostCombined(a->distance_, b->distance_, + NUM_DISTANCE_CODES); + if (*cost > cost_threshold) return 0; + + return 1; +} - -static double BitsEntropy(const int* const array, int n) { - double retval = 0.; - int sum = 0; - int nonzeros = 0; - int max_val = 0; - int i; - 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]; - } - } +// 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_; + out->trivial_symbol_ = (a->trivial_symbol_ == b->trivial_symbol_) ? + a->trivial_symbol_ : VP8L_NON_TRIVIAL_SYM; } - retval += VP8LFastSLog2(sum); - 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; - } + return cost - sum_cost; +} - { - double min_limit = 2 * sum - max_val; - min_limit = mix * min_limit + (1.0 - mix) * retval; - return (retval < min_limit) ? min_limit : retval; - } +// 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; } -double VP8LHistogramEstimateBitsBulk(const VP8LHistogram* const p) { - double retval = BitsEntropy(&p->literal_[0], VP8LHistogramNumCodes(p)) - + BitsEntropy(&p->red_[0], 256) - + BitsEntropy(&p->blue_[0], 256) - + BitsEntropy(&p->alpha_[0], 256) - + BitsEntropy(&p->distance_[0], NUM_DISTANCE_CODES); - // Compute the extra bits cost. - int i; - for (i = 2; i < NUM_LENGTH_CODES - 2; ++i) { - retval += - (i >> 1) * p->literal_[256 + i + 2]; - } - for (i = 2; i < NUM_DISTANCE_CODES - 2; ++i) { - retval += (i >> 1) * p->distance_[i + 2]; - } - return retval; -} - - -// 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; - } - } - streak = 0; - } - if (i == length - 1) { - ++streak; - goto last_streak_hack; +// ----------------------------------------------------------------------------- + +// 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) { + uint32_t alpha_sym, red_sym, blue_sym; + const double alpha_cost = VP8LPopulationCost(h->alpha_, NUM_LITERAL_CODES, + &alpha_sym); + const double distance_cost = + VP8LPopulationCost(h->distance_, NUM_DISTANCE_CODES, NULL) + + VP8LExtraCost(h->distance_, NUM_DISTANCE_CODES); + const int num_codes = VP8LHistogramNumCodes(h->palette_code_bits_); + h->literal_cost_ = VP8LPopulationCost(h->literal_, num_codes, NULL) + + VP8LExtraCost(h->literal_ + NUM_LITERAL_CODES, + NUM_LENGTH_CODES); + h->red_cost_ = VP8LPopulationCost(h->red_, NUM_LITERAL_CODES, &red_sym); + h->blue_cost_ = VP8LPopulationCost(h->blue_, NUM_LITERAL_CODES, &blue_sym); + h->bit_cost_ = h->literal_cost_ + h->red_cost_ + h->blue_cost_ + + alpha_cost + distance_cost; + if ((alpha_sym | red_sym | blue_sym) == VP8L_NON_TRIVIAL_SYM) { + h->trivial_symbol_ = VP8L_NON_TRIVIAL_SYM; + } else { + h->trivial_symbol_ = + ((uint32_t)alpha_sym << 24) | (red_sym << 16) | (blue_sym << 0); } - return retval; } -// Estimates the Huffman dictionary + other block overhead size. -static double HistogramEstimateBitsHeader(const VP8LHistogram* const p) { - return HuffmanCost(&p->alpha_[0], 256) + - HuffmanCost(&p->red_[0], 256) + - HuffmanCost(&p->literal_[0], VP8LHistogramNumCodes(p)) + - HuffmanCost(&p->blue_[0], 256) + - HuffmanCost(&p->distance_[0], NUM_DISTANCE_CODES); +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); } -double VP8LHistogramEstimateBits(const VP8LHistogram* const p) { - return HistogramEstimateBitsHeader(p) + VP8LHistogramEstimateBitsBulk(p); +static int GetHistoBinIndexLowEffort( + const VP8LHistogram* const h, const DominantCostRange* const c) { + const int bin_id = GetBinIdForEntropy(c->literal_min_, c->literal_max_, + h->literal_cost_); + assert(bin_id < NUM_PARTITIONS); + return bin_id; } -static void HistogramBuildImage(int xsize, int histo_bits, - const VP8LBackwardRefs* const backward_refs, - VP8LHistogramSet* const image) { - int i; +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]; + 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); @@ -237,7 +328,134 @@ 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 low_effort) { + 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 = low_effort ? + (int16_t)GetHistoBinIndexLowEffort(histo, &cost_range) : + (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 removing unused entries. +static void HistogramCompactBins(VP8LHistogramSet* const image_histo) { + VP8LHistogram** const histograms = image_histo->histograms; + int i, j; + + for (i = 0, j = 0; i < image_histo->size; ++i) { + if (histograms[i] != NULL && histograms[i]->bit_cost_ != 0.) { + if (j < i) { + histograms[j] = histograms[i]; + histograms[i] = NULL; + } + ++j; + } } + image_histo->size = j; +} + +static VP8LHistogram* HistogramCombineEntropyBin( + VP8LHistogramSet* const image_histo, + VP8LHistogram* cur_combo, + int16_t* const bin_map, int bin_depth, int num_bins, + double combine_cost_factor, int low_effort) { + int bin_id; + VP8LHistogram** const histograms = image_histo->histograms; + + for (bin_id = 0; bin_id < num_bins; ++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 num_combine_failures = 0; + int n; + for (n = 2; n <= num_histos; ++n) { + const int idx2 = bin_map[bin_offset + n]; + if (low_effort) { + // Merge all histograms with the same bin index, irrespective of cost of + // the merged histograms. + VP8LHistogramAdd(histograms[idx1], histograms[idx2], histograms[idx1]); + histograms[idx2]->bit_cost_ = 0.; + } else { + 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) { + // Try to merge two histograms only if the combo is a trivial one or + // the two candidate histograms are already non-trivial. + // For some images, 'try_combine' turns out to be false for a lot of + // histogram pairs. In that case, we fallback to combining + // histograms as usual to avoid increasing the header size. + const int try_combine = + (cur_combo->trivial_symbol_ != VP8L_NON_TRIVIAL_SYM) || + ((histograms[idx1]->trivial_symbol_ == VP8L_NON_TRIVIAL_SYM) && + (histograms[idx2]->trivial_symbol_ == VP8L_NON_TRIVIAL_SYM)); + const int max_combine_failures = 32; + if (try_combine || (num_combine_failures >= max_combine_failures)) { + HistogramSwap(&cur_combo, &histograms[idx1]); + histograms[idx2]->bit_cost_ = 0.; + } else { + ++num_combine_failures; + } + } + } + } + } + if (low_effort) { + // Update the bit_cost for the merged histograms (per bin index). + UpdateHistogramCost(histograms[idx1]); + } + } + HistogramCompactBins(image_histo); + return cur_combo; } static uint32_t MyRand(uint32_t *seed) { @@ -248,159 +466,433 @@ static uint32_t MyRand(uint32_t *seed) { return *seed; } -static int HistogramCombine(const VP8LHistogramSet* const in, - VP8LHistogramSet* const out, int num_pairs) { +// ----------------------------------------------------------------------------- +// Histogram pairs priority queue + +// Pair of histograms. Negative idx1 value means that pair is out-of-date. +typedef struct { + int idx1; + int idx2; + double cost_diff; + double cost_combo; +} HistogramPair; + +typedef struct { + HistogramPair* heap; + int* positions; + int size; + int max_index; +} HistoHeap; + +static int HistoHeapInit(HistoHeap* const histo_heap, const int max_index) { + histo_heap->size = 0; + histo_heap->max_index = max_index; + histo_heap->heap = WebPSafeMalloc(max_index * max_index, + sizeof(*histo_heap->heap)); + histo_heap->positions = WebPSafeMalloc(max_index * max_index, + sizeof(*histo_heap->positions)); + return histo_heap->heap != NULL && histo_heap->positions != NULL; +} + +static void HistoHeapClear(HistoHeap* const histo_heap) { + assert(histo_heap != NULL); + WebPSafeFree(histo_heap->heap); + WebPSafeFree(histo_heap->positions); +} + +static void SwapHistogramPairs(HistogramPair *p1, + HistogramPair *p2) { + const HistogramPair tmp = *p1; + *p1 = *p2; + *p2 = tmp; +} + +// Given a valid min-heap in range [0, heap_size-1) this function places value +// heap[heap_size-1] into right location within heap and sets its position in +// positions array. +static void HeapPush(HistoHeap* const histo_heap) { + HistogramPair* const heap = histo_heap->heap - 1; + int* const positions = histo_heap->positions; + const int max_index = histo_heap->max_index; + int v; + ++histo_heap->size; + v = histo_heap->size; + while (v > 1 && heap[v].cost_diff < heap[v >> 1].cost_diff) { + SwapHistogramPairs(&heap[v], &heap[v >> 1]); + // Change position of moved pair in heap. + if (heap[v].idx1 >= 0) { + const int pos = heap[v].idx1 * max_index + heap[v].idx2; + assert(pos >= 0 && pos < max_index * max_index); + positions[pos] = v; + } + v >>= 1; + } + positions[heap[v].idx1 * max_index + heap[v].idx2] = v; +} + +// Given a valid min-heap in range [0, heap_size) this function shortens heap +// range by one and places element with the lowest value to (heap_size-1). +static void HeapPop(HistoHeap* const histo_heap) { + HistogramPair* const heap = histo_heap->heap - 1; + int* const positions = histo_heap->positions; + const int heap_size = histo_heap->size; + const int max_index = histo_heap->max_index; + int v = 1; + if (heap[v].idx1 >= 0) { + positions[heap[v].idx1 * max_index + heap[v].idx2] = -1; + } + SwapHistogramPairs(&heap[v], &heap[heap_size]); + while ((v << 1) < heap_size) { + int son = (heap[v << 1].cost_diff < heap[v].cost_diff) ? (v << 1) : v; + if (((v << 1) + 1) < heap_size && + heap[(v << 1) + 1].cost_diff < heap[son].cost_diff) { + son = (v << 1) + 1; + } + if (son == v) break; + SwapHistogramPairs(&heap[v], &heap[son]); + // Change position of moved pair in heap. + if (heap[v].idx1 >= 0) { + positions[heap[v].idx1 * max_index + heap[v].idx2] = v; + } + v = son; + } + if (heap[v].idx1 >= 0) { + positions[heap[v].idx1 * max_index + heap[v].idx2] = v; + } + --histo_heap->size; +} + +// ----------------------------------------------------------------------------- + +static void PreparePair(VP8LHistogram** histograms, int idx1, int idx2, + HistogramPair* const pair, + VP8LHistogram* const histos) { + if (idx1 > idx2) { + const int tmp = idx2; + idx2 = idx1; + idx1 = tmp; + } + pair->idx1 = idx1; + pair->idx2 = idx2; + pair->cost_diff = + HistogramAddEval(histograms[idx1], histograms[idx2], histos, 0); + pair->cost_combo = histos->bit_cost_; +} + +#define POSITION_INVALID (-1) + +// Invalidates pairs intersecting (idx1, idx2) in heap. +static void InvalidatePairs(int idx1, int idx2, + const HistoHeap* const histo_heap) { + HistogramPair* const heap = histo_heap->heap - 1; + int* const positions = histo_heap->positions; + const int max_index = histo_heap->max_index; + int i; + for (i = 0; i < idx1; ++i) { + const int pos = positions[i * max_index + idx1]; + if (pos >= 0) { + heap[pos].idx1 = POSITION_INVALID; + } + } + for (i = idx1 + 1; i < max_index; ++i) { + const int pos = positions[idx1 * max_index + i]; + if (pos >= 0) { + heap[pos].idx1 = POSITION_INVALID; + } + } + for (i = 0; i < idx2; ++i) { + const int pos = positions[i * max_index + idx2]; + if (pos >= 0) { + heap[pos].idx1 = POSITION_INVALID; + } + } + for (i = idx2 + 1; i < max_index; ++i) { + const int pos = positions[idx2 * max_index + i]; + if (pos >= 0) { + heap[pos].idx1 = POSITION_INVALID; + } + } +} + +// Combines histograms by continuously choosing the one with the highest cost +// reduction. +static int HistogramCombineGreedy(VP8LHistogramSet* const image_histo, + VP8LHistogram* const histos) { int ok = 0; - int i, iter; + int image_histo_size = image_histo->size; + int i, j; + VP8LHistogram** const histograms = image_histo->histograms; + // Indexes of remaining histograms. + int* const clusters = WebPSafeMalloc(image_histo_size, sizeof(*clusters)); + // Heap of histogram pairs. + HistoHeap histo_heap; + + if (!HistoHeapInit(&histo_heap, image_histo_size) || clusters == NULL) { + goto End; + } + + for (i = 0; i < image_histo_size; ++i) { + // Initialize clusters indexes. + clusters[i] = i; + for (j = i + 1; j < image_histo_size; ++j) { + // Initialize positions array. + histo_heap.positions[i * histo_heap.max_index + j] = POSITION_INVALID; + PreparePair(histograms, i, j, &histo_heap.heap[histo_heap.size], histos); + if (histo_heap.heap[histo_heap.size].cost_diff < 0) { + HeapPush(&histo_heap); + } + } + } + + while (image_histo_size > 1 && histo_heap.size > 0) { + const int idx1 = histo_heap.heap[0].idx1; + const int idx2 = histo_heap.heap[0].idx2; + VP8LHistogramAdd(histograms[idx2], histograms[idx1], histograms[idx1]); + histograms[idx1]->bit_cost_ = histo_heap.heap[0].cost_combo; + // Remove merged histogram. + for (i = 0; i + 1 < image_histo_size; ++i) { + if (clusters[i] >= idx2) { + clusters[i] = clusters[i + 1]; + } + } + --image_histo_size; + + // Invalidate pairs intersecting the just combined best pair. + InvalidatePairs(idx1, idx2, &histo_heap); + + // Pop invalid pairs from the top of the heap. + while (histo_heap.size > 0 && histo_heap.heap[0].idx1 < 0) { + HeapPop(&histo_heap); + } + + // Push new pairs formed with combined histogram to the heap. + for (i = 0; i < image_histo_size; ++i) { + if (clusters[i] != idx1) { + PreparePair(histograms, idx1, clusters[i], + &histo_heap.heap[histo_heap.size], histos); + if (histo_heap.heap[histo_heap.size].cost_diff < 0) { + HeapPush(&histo_heap); + } + } + } + } + // Move remaining histograms to the beginning of the array. + for (i = 0; i < image_histo_size; ++i) { + if (i != clusters[i]) { // swap the two histograms + HistogramSwap(&histograms[i], &histograms[clusters[i]]); + } + } + + image_histo->size = image_histo_size; + ok = 1; + + End: + WebPSafeFree(clusters); + HistoHeapClear(&histo_heap); + return ok; +} + +static VP8LHistogram* HistogramCombineStochastic( + VP8LHistogramSet* const image_histo, + VP8LHistogram* tmp_histo, + VP8LHistogram* best_combo, + int quality, int min_cluster_size) { + int iter; uint32_t seed = 0; int tries_with_no_success = 0; - const int min_cluster_size = 2; - int out_size = in->size; - const int outer_iters = in->size * 3; - 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) { - // We pick the best pair to be combined out of 'inner_iters' pairs. + 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; + VP8LHistogram** const histograms = image_histo->histograms; + + // Collapse similar histograms in 'image_histo'. + ++min_cluster_size; + for (iter = 0; + iter < outer_iters && image_histo_size >= min_cluster_size; + ++iter) { double best_cost_diff = 0.; - int best_idx1 = 0, best_idx2 = 1; + 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_pairs; ++j) { + 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 tmp = ((j & 7) + 1) % (out_size - 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 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; } - *cur_combo = *out->histograms[idx1]; - VP8LHistogramAdd(cur_combo, out->histograms[idx2]); - cur_combo->bit_cost_ = VP8LHistogramEstimateBits(cur_combo); + // Calculate cost reduction on combining. - curr_cost_diff = cur_combo->bit_cost_ - - out->histograms[idx1]->bit_cost_ - - out->histograms[idx2]->bit_cost_; - if (best_cost_diff > curr_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; - } + curr_cost_diff = HistogramAddEval(histograms[idx1], histograms[idx2], + tmp_histo, best_cost_diff); + if (curr_cost_diff < best_cost_diff) { // found a better pair? + HistogramSwap(&best_combo, &tmp_histo); best_cost_diff = curr_cost_diff; best_idx1 = idx1; best_idx2 = idx2; } } - if (best_cost_diff < 0.0) { - *out->histograms[best_idx1] = *best_combo; + if (best_idx1 >= 0) { + HistogramSwap(&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) { + HistogramSwap(&histograms[image_histo_size], &histograms[best_idx2]); + histograms[image_histo_size] = NULL; } tries_with_no_success = 0; } - if (++tries_with_no_success >= 50) { + if (++tries_with_no_success >= num_tries_no_success) { break; } } - out->size = out_size; - ok = 1; - - End: - free(histos); - return ok; + image_histo->size = image_histo_size; + return best_combo; } // ----------------------------------------------------------------------------- // Histogram refinement -// What is the bit cost of moving square_histogram from -// cur_symbol to candidate_symbol. -// TODO(skal): we don't really need to copy the histogram and Add(). Instead -// we just need VP8LDualHistogramEstimateBits(A, B) estimation function. -static double HistogramDistance(const VP8LHistogram* const square_histogram, - const VP8LHistogram* const candidate) { - const double previous_bit_cost = candidate->bit_cost_; - double new_bit_cost; - VP8LHistogram modified_histo; - modified_histo = *candidate; - VP8LHistogramAdd(&modified_histo, square_histogram); - new_bit_cost = VP8LHistogramEstimateBits(&modified_histo); - - return new_bit_cost - previous_bit_cost; -} - // 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) { - int best_out = 0; - double best_bits = HistogramDistance(in->histograms[i], out->histograms[0]); - int k; - for (k = 1; k < out->size; ++k) { - const double cur_bits = - HistogramDistance(in->histograms[i], out->histograms[k]); - if (cur_bits < best_bits) { - best_bits = cur_bits; - best_out = k; + VP8LHistogram** const orig_histograms = orig_histo->histograms; + VP8LHistogram** const histograms = image_histo->histograms; + const int orig_histo_size = orig_histo->size; + const int image_histo_size = image_histo->size; + if (image_histo_size > 1) { + 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; + } + } else { + assert(image_histo_size == 1); + for (i = 0; i < orig_histo_size; ++i) { + symbols[i] = 0; } - symbols[i] = best_out; } // 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) { - VP8LHistogramAdd(out->histograms[symbols[i]], in->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 (quality < 90) { + 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, + int quality, int low_effort, + int histo_bits, int cache_bits, + VP8LHistogramSet* const image_histo, + VP8LHistogramSet* const tmp_histos, 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 num_histo_pairs = 10 + quality / 2; // For HistogramCombine(). - const int histo_image_raw_size = histo_xsize * histo_ysize; - 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, num_histo_pairs)) { - goto Error; + const int image_histo_raw_size = histo_xsize * histo_ysize; + const int entropy_combine_num_bins = low_effort ? NUM_PARTITIONS : BIN_SIZE; + + // 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] = unused indices. + const int bin_depth = image_histo_raw_size + 1; + int16_t* bin_map = NULL; + VP8LHistogramSet* const orig_histo = + VP8LAllocateHistogramSet(image_histo_raw_size, cache_bits); + VP8LHistogram* cur_combo; + const int entropy_combine = + (orig_histo->size > entropy_combine_num_bins * 2) && (quality < 100); + + if (orig_histo == NULL) goto Error; + + // Don't attempt linear bin-partition heuristic for: + // histograms of small sizes, as bin_map will be very sparse and; + // Maximum quality (q==100), to preserve the compression gains at that level. + if (entropy_combine) { + const int bin_map_size = bin_depth * entropy_combine_num_bins; + 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); + + cur_combo = tmp_histos->histograms[1]; // pick up working slot + if (entropy_combine) { + const double combine_cost_factor = + GetCombineCostFactor(image_histo_raw_size, quality); + HistogramAnalyzeEntropyBin(orig_histo, bin_map, low_effort); + // Collapse histograms with similar entropy. + cur_combo = HistogramCombineEntropyBin(image_histo, cur_combo, bin_map, + bin_depth, entropy_combine_num_bins, + combine_cost_factor, low_effort); + } + + // Don't combine the histograms using stochastic and greedy heuristics for + // low-effort compression mode. + if (!low_effort || !entropy_combine) { + const float x = quality / 100.f; + // cubic ramp between 1 and MAX_HISTO_GREEDY: + const int threshold_size = (int)(1 + (x * x * x) * (MAX_HISTO_GREEDY - 1)); + cur_combo = HistogramCombineStochastic(image_histo, + tmp_histos->histograms[0], + cur_combo, quality, threshold_size); + if ((image_histo->size <= threshold_size) && + !HistogramCombineGreedy(image_histo, cur_combo)) { + goto Error; + } + } + + // TODO(vikasa): Optimize HistogramRemap for low-effort compression mode also. // 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); return ok; } |