diff options
Diffstat (limited to 'src/3rdparty/libwebp/src/enc/histogram.c')
| -rw-r--r-- | src/3rdparty/libwebp/src/enc/histogram.c | 564 |
1 files changed, 381 insertions, 183 deletions
diff --git a/src/3rdparty/libwebp/src/enc/histogram.c b/src/3rdparty/libwebp/src/enc/histogram.c index a2266b4..869882d 100644 --- a/src/3rdparty/libwebp/src/enc/histogram.c +++ b/src/3rdparty/libwebp/src/enc/histogram.c @@ -20,9 +20,6 @@ #include "../dsp/lossless.h" #include "../utils/utils.h" -#define ALIGN_CST 15 -#define DO_ALIGN(PTR) ((uintptr_t)((PTR) + ALIGN_CST) & ~ALIGN_CST) - #define MAX_COST 1.e38 // Number of partitions for the three dominant (literal, red and blue) symbol @@ -30,6 +27,8 @@ #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) { uint32_t* const literal = p->literal_; @@ -40,6 +39,13 @@ static void HistogramClear(VP8LHistogram* const p) { 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_; @@ -106,7 +112,8 @@ VP8LHistogramSet* VP8LAllocateHistogramSet(int size, int cache_bits) { VP8LHistogramSet* set; const int histo_size = VP8LGetHistogramSize(cache_bits); const size_t total_size = - sizeof(*set) + size * (sizeof(*set->histograms) + histo_size + ALIGN_CST); + 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; @@ -117,7 +124,7 @@ VP8LHistogramSet* VP8LAllocateHistogramSet(int size, int cache_bits) { set->max_size = size; set->size = size; for (i = 0; i < size; ++i) { - memory = (uint8_t*)DO_ALIGN(memory); + 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)); @@ -149,24 +156,26 @@ void VP8LHistogramAddSinglePixOrCopy(VP8LHistogram* const histo, } } -static WEBP_INLINE double BitsEntropyRefine(int nonzeros, int sum, int max_val, - double retval) { +// ----------------------------------------------------------------------------- +// Entropy-related functions. + +static WEBP_INLINE double BitsEntropyRefine(const VP8LBitEntropy* entropy) { double mix; - if (nonzeros < 5) { - if (nonzeros <= 1) { + if (entropy->nonzeros < 5) { + if (entropy->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; + if (entropy->nonzeros == 2) { + return 0.99 * entropy->sum + 0.01 * entropy->entropy; } // 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) { + if (entropy->nonzeros == 3) { mix = 0.95; } else { mix = 0.7; // nonzeros == 4. @@ -176,52 +185,22 @@ static WEBP_INLINE double BitsEntropyRefine(int nonzeros, int sum, int max_val, } { - double min_limit = 2 * sum - max_val; - min_limit = mix * min_limit + (1.0 - mix) * retval; - return (retval < min_limit) ? min_limit : retval; + double min_limit = 2 * entropy->sum - entropy->max_val; + min_limit = mix * min_limit + (1.0 - mix) * entropy->entropy; + return (entropy->entropy < min_limit) ? min_limit : entropy->entropy; } } -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]; - } - } +double VP8LBitsEntropy(const uint32_t* const array, int n, + uint32_t* const trivial_symbol) { + VP8LBitEntropy entropy; + VP8LBitsEntropyUnrefined(array, n, &entropy); + if (trivial_symbol != NULL) { + *trivial_symbol = + (entropy.nonzeros == 1) ? entropy.nonzero_code : VP8L_NON_TRIVIAL_SYM; } - 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); + return BitsEntropyRefine(&entropy); } static double InitialHuffmanCost(void) { @@ -242,47 +221,40 @@ static double FinalHuffmanCost(const VP8LStreaks* const stats) { return retval; } -// Trampolines -static double HuffmanCost(const uint32_t* const population, int length) { - const VP8LStreaks stats = VP8LHuffmanCostCount(population, length); - return FinalHuffmanCost(&stats); -} +// Get the symbol entropy for the distribution 'population'. +// Set 'trivial_sym', if there's only one symbol present in the distribution. +static double PopulationCost(const uint32_t* const population, int length, + uint32_t* const trivial_sym) { + VP8LBitEntropy bit_entropy; + VP8LStreaks stats; + VP8LGetEntropyUnrefined(population, length, &bit_entropy, &stats); + if (trivial_sym != NULL) { + *trivial_sym = (bit_entropy.nonzeros == 1) ? bit_entropy.nonzero_code + : VP8L_NON_TRIVIAL_SYM; + } -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); + return BitsEntropyRefine(&bit_entropy) + FinalHuffmanCost(&stats); } -// Aggregated costs -static double PopulationCost(const uint32_t* const population, int length) { - return BitsEntropy(population, length) + HuffmanCost(population, length); -} +static WEBP_INLINE double GetCombinedEntropy(const uint32_t* const X, + const uint32_t* const Y, + int length) { + VP8LBitEntropy bit_entropy; + VP8LStreaks stats; + VP8LGetCombinedEntropyUnrefined(X, Y, length, &bit_entropy, &stats); -static double GetCombinedEntropy(const uint32_t* const X, - const uint32_t* const Y, int length) { - return BitsEntropyCombined(X, Y, length) + HuffmanCostCombined(X, Y, length); + return BitsEntropyRefine(&bit_entropy) + FinalHuffmanCost(&stats); } // 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) + PopulationCost( + p->literal_, VP8LHistogramNumCodes(p->palette_code_bits_), NULL) + + PopulationCost(p->red_, NUM_LITERAL_CODES, NULL) + + PopulationCost(p->blue_, NUM_LITERAL_CODES, NULL) + + PopulationCost(p->alpha_, NUM_LITERAL_CODES, NULL) + + PopulationCost(p->distance_, NUM_DISTANCE_CODES, NULL) + VP8LExtraCost(p->literal_ + NUM_LITERAL_CODES, NUM_LENGTH_CODES) + VP8LExtraCost(p->distance_, NUM_DISTANCE_CODES); } @@ -313,8 +285,8 @@ static int GetCombinedHistogramEntropy(const VP8LHistogram* const a, if (*cost > cost_threshold) return 0; *cost += GetCombinedEntropy(a->distance_, b->distance_, NUM_DISTANCE_CODES); - *cost += VP8LExtraCostCombined(a->distance_, b->distance_, - NUM_DISTANCE_CODES); + *cost += + VP8LExtraCostCombined(a->distance_, b->distance_, NUM_DISTANCE_CODES); if (*cost > cost_threshold) return 0; return 1; @@ -338,6 +310,8 @@ static double HistogramAddEval(const VP8LHistogram* const a, 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; } return cost - sum_cost; @@ -389,18 +363,26 @@ static void UpdateDominantCostRange( } static void UpdateHistogramCost(VP8LHistogram* const h) { - const double alpha_cost = PopulationCost(h->alpha_, NUM_LITERAL_CODES); + uint32_t alpha_sym, red_sym, blue_sym; + const double alpha_cost = + PopulationCost(h->alpha_, NUM_LITERAL_CODES, &alpha_sym); const double distance_cost = - PopulationCost(h->distance_, NUM_DISTANCE_CODES) + + PopulationCost(h->distance_, NUM_DISTANCE_CODES, NULL) + VP8LExtraCost(h->distance_, NUM_DISTANCE_CODES); const int num_codes = VP8LHistogramNumCodes(h->palette_code_bits_); - h->literal_cost_ = PopulationCost(h->literal_, num_codes) + + h->literal_cost_ = PopulationCost(h->literal_, num_codes, NULL) + 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->red_cost_ = PopulationCost(h->red_, NUM_LITERAL_CODES, &red_sym); + h->blue_cost_ = PopulationCost(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); + } } static int GetBinIdForEntropy(double min, double max, double val) { @@ -409,7 +391,14 @@ static int GetBinIdForEntropy(double min, double max, double val) { return (int)(NUM_PARTITIONS * delta / range); } -// TODO(vikasa): Evaluate, if there's any correlation between red & blue. +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 int GetHistoBinIndex( const VP8LHistogram* const h, const DominantCostRange* const c) { const int bin_id = @@ -432,7 +421,6 @@ static void HistogramBuild( 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); @@ -463,8 +451,8 @@ static void HistogramCopyAndAnalyze( // 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) { +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; @@ -483,7 +471,9 @@ static void HistogramAnalyzeEntropyBin( 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 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. @@ -495,64 +485,79 @@ static void HistogramAnalyzeEntropyBin( } } -// 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. +// Compact the histogram set by removing unused entries. 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; + 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 = end + 1; + image_histo->size = j; } -static void HistogramCombineEntropyBin(VP8LHistogramSet* const image_histo, - VP8LHistogram* const histos, - int16_t* const bin_map, int bin_depth, - double combine_cost_factor) { +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* cur_combo = histos; VP8LHistogram** const histograms = image_histo->histograms; - for (bin_id = 0; bin_id < BIN_SIZE; ++bin_id) { + 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]; - 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.; + 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) { @@ -563,8 +568,179 @@ static uint32_t MyRand(uint32_t *seed) { return *seed; } -static void HistogramCombine(VP8LHistogramSet* const image_histo, - VP8LHistogramSet* const histos, int quality) { +// ----------------------------------------------------------------------------- +// 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* queue; + int size; + int max_size; +} HistoQueue; + +static int HistoQueueInit(HistoQueue* const histo_queue, const int max_index) { + histo_queue->size = 0; + // max_index^2 for the queue size is safe. If you look at + // HistogramCombineGreedy, and imagine that UpdateQueueFront always pushes + // data to the queue, you insert at most: + // - max_index*(max_index-1)/2 (the first two for loops) + // - max_index - 1 in the last for loop at the first iteration of the while + // loop, max_index - 2 at the second iteration ... therefore + // max_index*(max_index-1)/2 overall too + histo_queue->max_size = max_index * max_index; + // We allocate max_size + 1 because the last element at index "size" is + // used as temporary data (and it could be up to max_size). + histo_queue->queue = WebPSafeMalloc(histo_queue->max_size + 1, + sizeof(*histo_queue->queue)); + return histo_queue->queue != NULL; +} + +static void HistoQueueClear(HistoQueue* const histo_queue) { + assert(histo_queue != NULL); + WebPSafeFree(histo_queue->queue); +} + +static void SwapHistogramPairs(HistogramPair *p1, + HistogramPair *p2) { + const HistogramPair tmp = *p1; + *p1 = *p2; + *p2 = tmp; +} + +// Given a valid priority queue in range [0, queue_size) this function checks +// whether histo_queue[queue_size] should be accepted and swaps it with the +// front if it is smaller. Otherwise, it leaves it as is. +static void UpdateQueueFront(HistoQueue* const histo_queue) { + if (histo_queue->queue[histo_queue->size].cost_diff >= 0) return; + + if (histo_queue->queue[histo_queue->size].cost_diff < + histo_queue->queue[0].cost_diff) { + SwapHistogramPairs(histo_queue->queue, + histo_queue->queue + histo_queue->size); + } + ++histo_queue->size; + + // We cannot add more elements than the capacity. + // The allocation adds an extra element to the official capacity so that + // histo_queue->queue[histo_queue->max_size] is read/written within bound. + assert(histo_queue->size <= histo_queue->max_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_; +} + +// 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 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)); + // Priority queue of histogram pairs. + HistoQueue histo_queue; + + if (!HistoQueueInit(&histo_queue, 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. + PreparePair(histograms, i, j, &histo_queue.queue[histo_queue.size], + histos); + UpdateQueueFront(&histo_queue); + } + } + + while (image_histo_size > 1 && histo_queue.size > 0) { + HistogramPair* copy_to; + const int idx1 = histo_queue.queue[0].idx1; + const int idx2 = histo_queue.queue[0].idx2; + VP8LHistogramAdd(histograms[idx2], histograms[idx1], histograms[idx1]); + histograms[idx1]->bit_cost_ = histo_queue.queue[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; + + // Remove pairs intersecting the just combined best pair. This will + // therefore pop the head of the queue. + copy_to = histo_queue.queue; + for (i = 0; i < histo_queue.size; ++i) { + HistogramPair* const p = histo_queue.queue + i; + if (p->idx1 == idx1 || p->idx2 == idx1 || + p->idx1 == idx2 || p->idx2 == idx2) { + // Do not copy the invalid pair. + continue; + } + if (p->cost_diff < histo_queue.queue[0].cost_diff) { + // Replace the top of the queue if we found better. + SwapHistogramPairs(histo_queue.queue, p); + } + SwapHistogramPairs(copy_to, p); + ++copy_to; + } + histo_queue.size = (int)(copy_to - histo_queue.queue); + + // Push new pairs formed with combined histogram to the queue. + for (i = 0; i < image_histo_size; ++i) { + if (clusters[i] != idx1) { + PreparePair(histograms, idx1, clusters[i], + &histo_queue.queue[histo_queue.size], histos); + UpdateQueueFront(&histo_queue); + } + } + } + // 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); + HistoQueueClear(&histo_queue); + 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; @@ -573,12 +749,10 @@ static void HistogramCombine(VP8LHistogramSet* const image_histo, 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'. + ++min_cluster_size; for (iter = 0; iter < outer_iters && image_histo_size >= min_cluster_size; ++iter) { @@ -602,13 +776,9 @@ static void HistogramCombine(VP8LHistogramSet* const image_histo, // Calculate cost reduction on combining. curr_cost_diff = HistogramAddEval(histograms[idx1], histograms[idx2], - cur_combo, best_cost_diff); + tmp_histo, 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; - } + HistogramSwap(&best_combo, &tmp_histo); best_cost_diff = curr_cost_diff; best_idx1 = idx1; best_idx2 = idx2; @@ -616,11 +786,11 @@ static void HistogramCombine(VP8LHistogramSet* const image_histo, } if (best_idx1 >= 0) { - HistogramCopy(best_combo, histograms[best_idx1]); + HistogramSwap(&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]); + HistogramSwap(&histograms[image_histo_size], &histograms[best_idx2]); histograms[image_histo_size] = NULL; } tries_with_no_success = 0; @@ -630,6 +800,7 @@ static void HistogramCombine(VP8LHistogramSet* const image_histo, } } image_histo->size = image_histo_size; + return best_combo; } // ----------------------------------------------------------------------------- @@ -643,28 +814,37 @@ static void HistogramRemap(const VP8LHistogramSet* const orig_histo, 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; + 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 < image_histo->size; ++i) { + for (i = 0; i < image_histo_size; ++i) { HistogramClear(histograms[i]); } - for (i = 0; i < orig_histo->size; ++i) { + for (i = 0; i < orig_histo_size; ++i) { const int idx = symbols[i]; VP8LHistogramAdd(orig_histograms[i], histograms[idx], histograms[idx]); } @@ -672,44 +852,48 @@ static void HistogramRemap(const VP8LHistogramSet* const orig_histo, 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.; + 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, + 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 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] = un-used indices. + // 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 histos = VP8LAllocateHistogramSet(2, cache_bits); 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 || histos == NULL) { - goto Error; - } + 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; - // 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; + // 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; } @@ -719,18 +903,33 @@ int VP8LGetHistoImageSymbols(int xsize, int ysize, // Copies the histograms and computes its bit_cost. HistogramCopyAndAnalyze(orig_histo, image_histo); - if (bin_map != NULL) { + 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); + HistogramAnalyzeEntropyBin(orig_histo, bin_map, low_effort); // Collapse histograms with similar entropy. - HistogramCombineEntropyBin(image_histo, histos->histograms[0], - bin_map, bin_depth, combine_cost_factor); + cur_combo = HistogramCombineEntropyBin(image_histo, cur_combo, bin_map, + bin_depth, entropy_combine_num_bins, + combine_cost_factor, low_effort); } - // Collapse similar histograms by random histogram-pair compares. - HistogramCombine(image_histo, histos, quality); + // 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(orig_histo, image_histo, histogram_symbols); @@ -739,6 +938,5 @@ int VP8LGetHistoImageSymbols(int xsize, int ysize, Error: WebPSafeFree(bin_map); VP8LFreeHistogramSet(orig_histo); - VP8LFreeHistogramSet(histos); return ok; } |