diff options
Diffstat (limited to 'media/libwebp/src/enc/backward_references_cost_enc.c')
| -rw-r--r-- | media/libwebp/src/enc/backward_references_cost_enc.c | 795 |
1 files changed, 795 insertions, 0 deletions
diff --git a/media/libwebp/src/enc/backward_references_cost_enc.c b/media/libwebp/src/enc/backward_references_cost_enc.c new file mode 100644 index 0000000000..6968ef3c9f --- /dev/null +++ b/media/libwebp/src/enc/backward_references_cost_enc.c @@ -0,0 +1,795 @@ +// Copyright 2017 Google Inc. All Rights Reserved. +// +// Use of this source code is governed by a BSD-style license +// that can be found in the COPYING file in the root of the source +// tree. An additional intellectual property rights grant can be found +// in the file PATENTS. All contributing project authors may +// be found in the AUTHORS file in the root of the source tree. +// ----------------------------------------------------------------------------- +// +// Improves a given set of backward references by analyzing its bit cost. +// The algorithm is similar to the Zopfli compression algorithm but tailored to +// images. +// +// Author: Vincent Rabaud (vrabaud@google.com) +// + +#include <assert.h> +#include <float.h> + +#include "src/dsp/lossless_common.h" +#include "src/enc/backward_references_enc.h" +#include "src/enc/histogram_enc.h" +#include "src/utils/color_cache_utils.h" +#include "src/utils/utils.h" + +#define VALUES_IN_BYTE 256 + +extern void VP8LClearBackwardRefs(VP8LBackwardRefs* const refs); +extern int VP8LDistanceToPlaneCode(int xsize, int dist); +extern void VP8LBackwardRefsCursorAdd(VP8LBackwardRefs* const refs, + const PixOrCopy v); + +typedef struct { + float alpha_[VALUES_IN_BYTE]; + float red_[VALUES_IN_BYTE]; + float blue_[VALUES_IN_BYTE]; + float distance_[NUM_DISTANCE_CODES]; + float* literal_; +} CostModel; + +static void ConvertPopulationCountTableToBitEstimates( + int num_symbols, const uint32_t population_counts[], float output[]) { + uint32_t sum = 0; + int nonzeros = 0; + int i; + for (i = 0; i < num_symbols; ++i) { + sum += population_counts[i]; + if (population_counts[i] > 0) { + ++nonzeros; + } + } + if (nonzeros <= 1) { + memset(output, 0, num_symbols * sizeof(*output)); + } else { + const float logsum = VP8LFastLog2(sum); + for (i = 0; i < num_symbols; ++i) { + output[i] = logsum - VP8LFastLog2(population_counts[i]); + } + } +} + +static int CostModelBuild(CostModel* const m, int xsize, int cache_bits, + const VP8LBackwardRefs* const refs) { + int ok = 0; + VP8LRefsCursor c = VP8LRefsCursorInit(refs); + VP8LHistogram* const histo = VP8LAllocateHistogram(cache_bits); + if (histo == NULL) goto Error; + + // The following code is similar to VP8LHistogramCreate but converts the + // distance to plane code. + VP8LHistogramInit(histo, cache_bits, /*init_arrays=*/ 1); + while (VP8LRefsCursorOk(&c)) { + VP8LHistogramAddSinglePixOrCopy(histo, c.cur_pos, VP8LDistanceToPlaneCode, + xsize); + VP8LRefsCursorNext(&c); + } + + ConvertPopulationCountTableToBitEstimates( + VP8LHistogramNumCodes(histo->palette_code_bits_), histo->literal_, + m->literal_); + ConvertPopulationCountTableToBitEstimates( + VALUES_IN_BYTE, histo->red_, m->red_); + ConvertPopulationCountTableToBitEstimates( + VALUES_IN_BYTE, histo->blue_, m->blue_); + ConvertPopulationCountTableToBitEstimates( + VALUES_IN_BYTE, histo->alpha_, m->alpha_); + ConvertPopulationCountTableToBitEstimates( + NUM_DISTANCE_CODES, histo->distance_, m->distance_); + ok = 1; + + Error: + VP8LFreeHistogram(histo); + return ok; +} + +static WEBP_INLINE float GetLiteralCost(const CostModel* const m, uint32_t v) { + return m->alpha_[v >> 24] + + m->red_[(v >> 16) & 0xff] + + m->literal_[(v >> 8) & 0xff] + + m->blue_[v & 0xff]; +} + +static WEBP_INLINE float GetCacheCost(const CostModel* const m, uint32_t idx) { + const int literal_idx = VALUES_IN_BYTE + NUM_LENGTH_CODES + idx; + return m->literal_[literal_idx]; +} + +static WEBP_INLINE float GetLengthCost(const CostModel* const m, + uint32_t length) { + int code, extra_bits; + VP8LPrefixEncodeBits(length, &code, &extra_bits); + return m->literal_[VALUES_IN_BYTE + code] + extra_bits; +} + +static WEBP_INLINE float GetDistanceCost(const CostModel* const m, + uint32_t distance) { + int code, extra_bits; + VP8LPrefixEncodeBits(distance, &code, &extra_bits); + return m->distance_[code] + extra_bits; +} + +static WEBP_INLINE void AddSingleLiteralWithCostModel( + const uint32_t* const argb, VP8LColorCache* const hashers, + const CostModel* const cost_model, int idx, int use_color_cache, + float prev_cost, float* const cost, uint16_t* const dist_array) { + float cost_val = prev_cost; + const uint32_t color = argb[idx]; + const int ix = use_color_cache ? VP8LColorCacheContains(hashers, color) : -1; + if (ix >= 0) { + // use_color_cache is true and hashers contains color + const float mul0 = 0.68f; + cost_val += GetCacheCost(cost_model, ix) * mul0; + } else { + const float mul1 = 0.82f; + if (use_color_cache) VP8LColorCacheInsert(hashers, color); + cost_val += GetLiteralCost(cost_model, color) * mul1; + } + if (cost[idx] > cost_val) { + cost[idx] = cost_val; + dist_array[idx] = 1; // only one is inserted. + } +} + +// ----------------------------------------------------------------------------- +// CostManager and interval handling + +// Empirical value to avoid high memory consumption but good for performance. +#define COST_CACHE_INTERVAL_SIZE_MAX 500 + +// To perform backward reference every pixel at index index_ is considered and +// the cost for the MAX_LENGTH following pixels computed. Those following pixels +// at index index_ + k (k from 0 to MAX_LENGTH) have a cost of: +// cost_ = distance cost at index + GetLengthCost(cost_model, k) +// and the minimum value is kept. GetLengthCost(cost_model, k) is cached in an +// array of size MAX_LENGTH. +// Instead of performing MAX_LENGTH comparisons per pixel, we keep track of the +// minimal values using intervals of constant cost. +// An interval is defined by the index_ of the pixel that generated it and +// is only useful in a range of indices from start_ to end_ (exclusive), i.e. +// it contains the minimum value for pixels between start_ and end_. +// Intervals are stored in a linked list and ordered by start_. When a new +// interval has a better value, old intervals are split or removed. There are +// therefore no overlapping intervals. +typedef struct CostInterval CostInterval; +struct CostInterval { + float cost_; + int start_; + int end_; + int index_; + CostInterval* previous_; + CostInterval* next_; +}; + +// The GetLengthCost(cost_model, k) are cached in a CostCacheInterval. +typedef struct { + float cost_; + int start_; + int end_; // Exclusive. +} CostCacheInterval; + +// This structure is in charge of managing intervals and costs. +// It caches the different CostCacheInterval, caches the different +// GetLengthCost(cost_model, k) in cost_cache_ and the CostInterval's (whose +// count_ is limited by COST_CACHE_INTERVAL_SIZE_MAX). +#define COST_MANAGER_MAX_FREE_LIST 10 +typedef struct { + CostInterval* head_; + int count_; // The number of stored intervals. + CostCacheInterval* cache_intervals_; + size_t cache_intervals_size_; + float cost_cache_[MAX_LENGTH]; // Contains the GetLengthCost(cost_model, k). + float* costs_; + uint16_t* dist_array_; + // Most of the time, we only need few intervals -> use a free-list, to avoid + // fragmentation with small allocs in most common cases. + CostInterval intervals_[COST_MANAGER_MAX_FREE_LIST]; + CostInterval* free_intervals_; + // These are regularly malloc'd remains. This list can't grow larger than than + // size COST_CACHE_INTERVAL_SIZE_MAX - COST_MANAGER_MAX_FREE_LIST, note. + CostInterval* recycled_intervals_; +} CostManager; + +static void CostIntervalAddToFreeList(CostManager* const manager, + CostInterval* const interval) { + interval->next_ = manager->free_intervals_; + manager->free_intervals_ = interval; +} + +static int CostIntervalIsInFreeList(const CostManager* const manager, + const CostInterval* const interval) { + return (interval >= &manager->intervals_[0] && + interval <= &manager->intervals_[COST_MANAGER_MAX_FREE_LIST - 1]); +} + +static void CostManagerInitFreeList(CostManager* const manager) { + int i; + manager->free_intervals_ = NULL; + for (i = 0; i < COST_MANAGER_MAX_FREE_LIST; ++i) { + CostIntervalAddToFreeList(manager, &manager->intervals_[i]); + } +} + +static void DeleteIntervalList(CostManager* const manager, + const CostInterval* interval) { + while (interval != NULL) { + const CostInterval* const next = interval->next_; + if (!CostIntervalIsInFreeList(manager, interval)) { + WebPSafeFree((void*)interval); + } // else: do nothing + interval = next; + } +} + +static void CostManagerClear(CostManager* const manager) { + if (manager == NULL) return; + + WebPSafeFree(manager->costs_); + WebPSafeFree(manager->cache_intervals_); + + // Clear the interval lists. + DeleteIntervalList(manager, manager->head_); + manager->head_ = NULL; + DeleteIntervalList(manager, manager->recycled_intervals_); + manager->recycled_intervals_ = NULL; + + // Reset pointers, count_ and cache_intervals_size_. + memset(manager, 0, sizeof(*manager)); + CostManagerInitFreeList(manager); +} + +static int CostManagerInit(CostManager* const manager, + uint16_t* const dist_array, int pix_count, + const CostModel* const cost_model) { + int i; + const int cost_cache_size = (pix_count > MAX_LENGTH) ? MAX_LENGTH : pix_count; + + manager->costs_ = NULL; + manager->cache_intervals_ = NULL; + manager->head_ = NULL; + manager->recycled_intervals_ = NULL; + manager->count_ = 0; + manager->dist_array_ = dist_array; + CostManagerInitFreeList(manager); + + // Fill in the cost_cache_. + // Has to be done in two passes due to a GCC bug on i686 + // related to https://gcc.gnu.org/bugzilla/show_bug.cgi?id=323 + for (i = 0; i < cost_cache_size; ++i) { + manager->cost_cache_[i] = GetLengthCost(cost_model, i); + } + manager->cache_intervals_size_ = 1; + for (i = 1; i < cost_cache_size; ++i) { + // Get the number of bound intervals. + if (manager->cost_cache_[i] != manager->cost_cache_[i - 1]) { + ++manager->cache_intervals_size_; + } + } + + // With the current cost model, we usually have below 20 intervals. + // The worst case scenario with a cost model would be if every length has a + // different cost, hence MAX_LENGTH but that is impossible with the current + // implementation that spirals around a pixel. + assert(manager->cache_intervals_size_ <= MAX_LENGTH); + manager->cache_intervals_ = (CostCacheInterval*)WebPSafeMalloc( + manager->cache_intervals_size_, sizeof(*manager->cache_intervals_)); + if (manager->cache_intervals_ == NULL) { + CostManagerClear(manager); + return 0; + } + + // Fill in the cache_intervals_. + { + CostCacheInterval* cur = manager->cache_intervals_; + + // Consecutive values in cost_cache_ are compared and if a big enough + // difference is found, a new interval is created and bounded. + cur->start_ = 0; + cur->end_ = 1; + cur->cost_ = manager->cost_cache_[0]; + for (i = 1; i < cost_cache_size; ++i) { + const float cost_val = manager->cost_cache_[i]; + if (cost_val != cur->cost_) { + ++cur; + // Initialize an interval. + cur->start_ = i; + cur->cost_ = cost_val; + } + cur->end_ = i + 1; + } + assert((size_t)(cur - manager->cache_intervals_) + 1 == + manager->cache_intervals_size_); + } + + manager->costs_ = (float*)WebPSafeMalloc(pix_count, sizeof(*manager->costs_)); + if (manager->costs_ == NULL) { + CostManagerClear(manager); + return 0; + } + // Set the initial costs_ high for every pixel as we will keep the minimum. + for (i = 0; i < pix_count; ++i) manager->costs_[i] = FLT_MAX; + + return 1; +} + +// Given the cost and the position that define an interval, update the cost at +// pixel 'i' if it is smaller than the previously computed value. +static WEBP_INLINE void UpdateCost(CostManager* const manager, int i, + int position, float cost) { + const int k = i - position; + assert(k >= 0 && k < MAX_LENGTH); + + if (manager->costs_[i] > cost) { + manager->costs_[i] = cost; + manager->dist_array_[i] = k + 1; + } +} + +// Given the cost and the position that define an interval, update the cost for +// all the pixels between 'start' and 'end' excluded. +static WEBP_INLINE void UpdateCostPerInterval(CostManager* const manager, + int start, int end, int position, + float cost) { + int i; + for (i = start; i < end; ++i) UpdateCost(manager, i, position, cost); +} + +// Given two intervals, make 'prev' be the previous one of 'next' in 'manager'. +static WEBP_INLINE void ConnectIntervals(CostManager* const manager, + CostInterval* const prev, + CostInterval* const next) { + if (prev != NULL) { + prev->next_ = next; + } else { + manager->head_ = next; + } + + if (next != NULL) next->previous_ = prev; +} + +// Pop an interval in the manager. +static WEBP_INLINE void PopInterval(CostManager* const manager, + CostInterval* const interval) { + if (interval == NULL) return; + + ConnectIntervals(manager, interval->previous_, interval->next_); + if (CostIntervalIsInFreeList(manager, interval)) { + CostIntervalAddToFreeList(manager, interval); + } else { // recycle regularly malloc'd intervals too + interval->next_ = manager->recycled_intervals_; + manager->recycled_intervals_ = interval; + } + --manager->count_; + assert(manager->count_ >= 0); +} + +// Update the cost at index i by going over all the stored intervals that +// overlap with i. +// If 'do_clean_intervals' is set to something different than 0, intervals that +// end before 'i' will be popped. +static WEBP_INLINE void UpdateCostAtIndex(CostManager* const manager, int i, + int do_clean_intervals) { + CostInterval* current = manager->head_; + + while (current != NULL && current->start_ <= i) { + CostInterval* const next = current->next_; + if (current->end_ <= i) { + if (do_clean_intervals) { + // We have an outdated interval, remove it. + PopInterval(manager, current); + } + } else { + UpdateCost(manager, i, current->index_, current->cost_); + } + current = next; + } +} + +// Given a current orphan interval and its previous interval, before +// it was orphaned (which can be NULL), set it at the right place in the list +// of intervals using the start_ ordering and the previous interval as a hint. +static WEBP_INLINE void PositionOrphanInterval(CostManager* const manager, + CostInterval* const current, + CostInterval* previous) { + assert(current != NULL); + + if (previous == NULL) previous = manager->head_; + while (previous != NULL && current->start_ < previous->start_) { + previous = previous->previous_; + } + while (previous != NULL && previous->next_ != NULL && + previous->next_->start_ < current->start_) { + previous = previous->next_; + } + + if (previous != NULL) { + ConnectIntervals(manager, current, previous->next_); + } else { + ConnectIntervals(manager, current, manager->head_); + } + ConnectIntervals(manager, previous, current); +} + +// Insert an interval in the list contained in the manager by starting at +// interval_in as a hint. The intervals are sorted by start_ value. +static WEBP_INLINE void InsertInterval(CostManager* const manager, + CostInterval* const interval_in, + float cost, int position, int start, + int end) { + CostInterval* interval_new; + + if (start >= end) return; + if (manager->count_ >= COST_CACHE_INTERVAL_SIZE_MAX) { + // Serialize the interval if we cannot store it. + UpdateCostPerInterval(manager, start, end, position, cost); + return; + } + if (manager->free_intervals_ != NULL) { + interval_new = manager->free_intervals_; + manager->free_intervals_ = interval_new->next_; + } else if (manager->recycled_intervals_ != NULL) { + interval_new = manager->recycled_intervals_; + manager->recycled_intervals_ = interval_new->next_; + } else { // malloc for good + interval_new = (CostInterval*)WebPSafeMalloc(1, sizeof(*interval_new)); + if (interval_new == NULL) { + // Write down the interval if we cannot create it. + UpdateCostPerInterval(manager, start, end, position, cost); + return; + } + } + + interval_new->cost_ = cost; + interval_new->index_ = position; + interval_new->start_ = start; + interval_new->end_ = end; + PositionOrphanInterval(manager, interval_new, interval_in); + + ++manager->count_; +} + +// Given a new cost interval defined by its start at position, its length value +// and distance_cost, add its contributions to the previous intervals and costs. +// If handling the interval or one of its subintervals becomes to heavy, its +// contribution is added to the costs right away. +static WEBP_INLINE void PushInterval(CostManager* const manager, + float distance_cost, int position, + int len) { + size_t i; + CostInterval* interval = manager->head_; + CostInterval* interval_next; + const CostCacheInterval* const cost_cache_intervals = + manager->cache_intervals_; + // If the interval is small enough, no need to deal with the heavy + // interval logic, just serialize it right away. This constant is empirical. + const int kSkipDistance = 10; + + if (len < kSkipDistance) { + int j; + for (j = position; j < position + len; ++j) { + const int k = j - position; + float cost_tmp; + assert(k >= 0 && k < MAX_LENGTH); + cost_tmp = distance_cost + manager->cost_cache_[k]; + + if (manager->costs_[j] > cost_tmp) { + manager->costs_[j] = cost_tmp; + manager->dist_array_[j] = k + 1; + } + } + return; + } + + for (i = 0; i < manager->cache_intervals_size_ && + cost_cache_intervals[i].start_ < len; + ++i) { + // Define the intersection of the ith interval with the new one. + int start = position + cost_cache_intervals[i].start_; + const int end = position + (cost_cache_intervals[i].end_ > len + ? len + : cost_cache_intervals[i].end_); + const float cost = distance_cost + cost_cache_intervals[i].cost_; + + for (; interval != NULL && interval->start_ < end; + interval = interval_next) { + interval_next = interval->next_; + + // Make sure we have some overlap + if (start >= interval->end_) continue; + + if (cost >= interval->cost_) { + // When intervals are represented, the lower, the better. + // [**********************************************************[ + // start end + // [----------------------------------[ + // interval->start_ interval->end_ + // If we are worse than what we already have, add whatever we have so + // far up to interval. + const int start_new = interval->end_; + InsertInterval(manager, interval, cost, position, start, + interval->start_); + start = start_new; + if (start >= end) break; + continue; + } + + if (start <= interval->start_) { + if (interval->end_ <= end) { + // [----------------------------------[ + // interval->start_ interval->end_ + // [**************************************************************[ + // start end + // We can safely remove the old interval as it is fully included. + PopInterval(manager, interval); + } else { + // [------------------------------------[ + // interval->start_ interval->end_ + // [*****************************[ + // start end + interval->start_ = end; + break; + } + } else { + if (end < interval->end_) { + // [--------------------------------------------------------------[ + // interval->start_ interval->end_ + // [*****************************[ + // start end + // We have to split the old interval as it fully contains the new one. + const int end_original = interval->end_; + interval->end_ = start; + InsertInterval(manager, interval, interval->cost_, interval->index_, + end, end_original); + interval = interval->next_; + break; + } else { + // [------------------------------------[ + // interval->start_ interval->end_ + // [*****************************[ + // start end + interval->end_ = start; + } + } + } + // Insert the remaining interval from start to end. + InsertInterval(manager, interval, cost, position, start, end); + } +} + +static int BackwardReferencesHashChainDistanceOnly( + int xsize, int ysize, const uint32_t* const argb, int cache_bits, + const VP8LHashChain* const hash_chain, const VP8LBackwardRefs* const refs, + uint16_t* const dist_array) { + int i; + int ok = 0; + int cc_init = 0; + const int pix_count = xsize * ysize; + const int use_color_cache = (cache_bits > 0); + const size_t literal_array_size = + sizeof(float) * (VP8LHistogramNumCodes(cache_bits)); + const size_t cost_model_size = sizeof(CostModel) + literal_array_size; + CostModel* const cost_model = + (CostModel*)WebPSafeCalloc(1ULL, cost_model_size); + VP8LColorCache hashers; + CostManager* cost_manager = + (CostManager*)WebPSafeCalloc(1ULL, sizeof(*cost_manager)); + int offset_prev = -1, len_prev = -1; + float offset_cost = -1.f; + int first_offset_is_constant = -1; // initialized with 'impossible' value + int reach = 0; + + if (cost_model == NULL || cost_manager == NULL) goto Error; + + cost_model->literal_ = (float*)(cost_model + 1); + if (use_color_cache) { + cc_init = VP8LColorCacheInit(&hashers, cache_bits); + if (!cc_init) goto Error; + } + + if (!CostModelBuild(cost_model, xsize, cache_bits, refs)) { + goto Error; + } + + if (!CostManagerInit(cost_manager, dist_array, pix_count, cost_model)) { + goto Error; + } + + // We loop one pixel at a time, but store all currently best points to + // non-processed locations from this point. + dist_array[0] = 0; + // Add first pixel as literal. + AddSingleLiteralWithCostModel(argb, &hashers, cost_model, 0, use_color_cache, + 0.f, cost_manager->costs_, dist_array); + + for (i = 1; i < pix_count; ++i) { + const float prev_cost = cost_manager->costs_[i - 1]; + int offset, len; + VP8LHashChainFindCopy(hash_chain, i, &offset, &len); + + // Try adding the pixel as a literal. + AddSingleLiteralWithCostModel(argb, &hashers, cost_model, i, + use_color_cache, prev_cost, + cost_manager->costs_, dist_array); + + // If we are dealing with a non-literal. + if (len >= 2) { + if (offset != offset_prev) { + const int code = VP8LDistanceToPlaneCode(xsize, offset); + offset_cost = GetDistanceCost(cost_model, code); + first_offset_is_constant = 1; + PushInterval(cost_manager, prev_cost + offset_cost, i, len); + } else { + assert(offset_cost >= 0); + assert(len_prev >= 0); + assert(first_offset_is_constant == 0 || first_offset_is_constant == 1); + // Instead of considering all contributions from a pixel i by calling: + // PushInterval(cost_manager, prev_cost + offset_cost, i, len); + // we optimize these contributions in case offset_cost stays the same + // for consecutive pixels. This describes a set of pixels similar to a + // previous set (e.g. constant color regions). + if (first_offset_is_constant) { + reach = i - 1 + len_prev - 1; + first_offset_is_constant = 0; + } + + if (i + len - 1 > reach) { + // We can only be go further with the same offset if the previous + // length was maxed, hence len_prev == len == MAX_LENGTH. + // TODO(vrabaud), bump i to the end right away (insert cache and + // update cost). + // TODO(vrabaud), check if one of the points in between does not have + // a lower cost. + // Already consider the pixel at "reach" to add intervals that are + // better than whatever we add. + int offset_j, len_j = 0; + int j; + assert(len == MAX_LENGTH || len == pix_count - i); + // Figure out the last consecutive pixel within [i, reach + 1] with + // the same offset. + for (j = i; j <= reach; ++j) { + VP8LHashChainFindCopy(hash_chain, j + 1, &offset_j, &len_j); + if (offset_j != offset) { + VP8LHashChainFindCopy(hash_chain, j, &offset_j, &len_j); + break; + } + } + // Update the cost at j - 1 and j. + UpdateCostAtIndex(cost_manager, j - 1, 0); + UpdateCostAtIndex(cost_manager, j, 0); + + PushInterval(cost_manager, cost_manager->costs_[j - 1] + offset_cost, + j, len_j); + reach = j + len_j - 1; + } + } + } + + UpdateCostAtIndex(cost_manager, i, 1); + offset_prev = offset; + len_prev = len; + } + + ok = !refs->error_; + Error: + if (cc_init) VP8LColorCacheClear(&hashers); + CostManagerClear(cost_manager); + WebPSafeFree(cost_model); + WebPSafeFree(cost_manager); + return ok; +} + +// We pack the path at the end of *dist_array and return +// a pointer to this part of the array. Example: +// dist_array = [1x2xx3x2] => packed [1x2x1232], chosen_path = [1232] +static void TraceBackwards(uint16_t* const dist_array, + int dist_array_size, + uint16_t** const chosen_path, + int* const chosen_path_size) { + uint16_t* path = dist_array + dist_array_size; + uint16_t* cur = dist_array + dist_array_size - 1; + while (cur >= dist_array) { + const int k = *cur; + --path; + *path = k; + cur -= k; + } + *chosen_path = path; + *chosen_path_size = (int)(dist_array + dist_array_size - path); +} + +static int BackwardReferencesHashChainFollowChosenPath( + const uint32_t* const argb, int cache_bits, + const uint16_t* const chosen_path, int chosen_path_size, + const VP8LHashChain* const hash_chain, VP8LBackwardRefs* const refs) { + const int use_color_cache = (cache_bits > 0); + int ix; + int i = 0; + int ok = 0; + int cc_init = 0; + VP8LColorCache hashers; + + if (use_color_cache) { + cc_init = VP8LColorCacheInit(&hashers, cache_bits); + if (!cc_init) goto Error; + } + + VP8LClearBackwardRefs(refs); + for (ix = 0; ix < chosen_path_size; ++ix) { + const int len = chosen_path[ix]; + if (len != 1) { + int k; + const int offset = VP8LHashChainFindOffset(hash_chain, i); + VP8LBackwardRefsCursorAdd(refs, PixOrCopyCreateCopy(offset, len)); + if (use_color_cache) { + for (k = 0; k < len; ++k) { + VP8LColorCacheInsert(&hashers, argb[i + k]); + } + } + i += len; + } else { + PixOrCopy v; + const int idx = + use_color_cache ? VP8LColorCacheContains(&hashers, argb[i]) : -1; + if (idx >= 0) { + // use_color_cache is true and hashers contains argb[i] + // push pixel as a color cache index + v = PixOrCopyCreateCacheIdx(idx); + } else { + if (use_color_cache) VP8LColorCacheInsert(&hashers, argb[i]); + v = PixOrCopyCreateLiteral(argb[i]); + } + VP8LBackwardRefsCursorAdd(refs, v); + ++i; + } + } + ok = !refs->error_; + Error: + if (cc_init) VP8LColorCacheClear(&hashers); + return ok; +} + +// Returns 1 on success. +extern int VP8LBackwardReferencesTraceBackwards( + int xsize, int ysize, const uint32_t* const argb, int cache_bits, + const VP8LHashChain* const hash_chain, + const VP8LBackwardRefs* const refs_src, VP8LBackwardRefs* const refs_dst); +int VP8LBackwardReferencesTraceBackwards(int xsize, int ysize, + const uint32_t* const argb, + int cache_bits, + const VP8LHashChain* const hash_chain, + const VP8LBackwardRefs* const refs_src, + VP8LBackwardRefs* const refs_dst) { + int ok = 0; + const int dist_array_size = xsize * ysize; + uint16_t* chosen_path = NULL; + int chosen_path_size = 0; + uint16_t* dist_array = + (uint16_t*)WebPSafeMalloc(dist_array_size, sizeof(*dist_array)); + + if (dist_array == NULL) goto Error; + + if (!BackwardReferencesHashChainDistanceOnly( + xsize, ysize, argb, cache_bits, hash_chain, refs_src, dist_array)) { + goto Error; + } + TraceBackwards(dist_array, dist_array_size, &chosen_path, &chosen_path_size); + if (!BackwardReferencesHashChainFollowChosenPath( + argb, cache_bits, chosen_path, chosen_path_size, hash_chain, + refs_dst)) { + goto Error; + } + ok = 1; + Error: + WebPSafeFree(dist_array); + return ok; +} |