diff options
Diffstat (limited to 'thirdparty/libwebp/enc/backward_references_enc.c')
| -rw-r--r-- | thirdparty/libwebp/enc/backward_references_enc.c | 1800 |
1 files changed, 1800 insertions, 0 deletions
diff --git a/thirdparty/libwebp/enc/backward_references_enc.c b/thirdparty/libwebp/enc/backward_references_enc.c new file mode 100644 index 0000000000..7c0559ff1e --- /dev/null +++ b/thirdparty/libwebp/enc/backward_references_enc.c @@ -0,0 +1,1800 @@ +// Copyright 2012 Google Inc. All Rights Reserved. +// +// Use of this source code is governed by a BSD-style license +// that can be found in the COPYING file in the root of the source +// tree. An additional intellectual property rights grant can be found +// in the file PATENTS. All contributing project authors may +// be found in the AUTHORS file in the root of the source tree. +// ----------------------------------------------------------------------------- +// +// Author: Jyrki Alakuijala (jyrki@google.com) +// + +#include <assert.h> +#include <math.h> + +#include "./backward_references_enc.h" +#include "./histogram_enc.h" +#include "../dsp/lossless.h" +#include "../dsp/lossless_common.h" +#include "../dsp/dsp.h" +#include "../utils/color_cache_utils.h" +#include "../utils/utils.h" + +#define VALUES_IN_BYTE 256 + +#define MIN_BLOCK_SIZE 256 // minimum block size for backward references + +#define MAX_ENTROPY (1e30f) + +// 1M window (4M bytes) minus 120 special codes for short distances. +#define WINDOW_SIZE_BITS 20 +#define WINDOW_SIZE ((1 << WINDOW_SIZE_BITS) - 120) + +// Minimum number of pixels for which it is cheaper to encode a +// distance + length instead of each pixel as a literal. +#define MIN_LENGTH 4 +// If you change this, you need MAX_LENGTH_BITS + WINDOW_SIZE_BITS <= 32 as it +// is used in VP8LHashChain. +#define MAX_LENGTH_BITS 12 +// We want the max value to be attainable and stored in MAX_LENGTH_BITS bits. +#define MAX_LENGTH ((1 << MAX_LENGTH_BITS) - 1) +#if MAX_LENGTH_BITS + WINDOW_SIZE_BITS > 32 +#error "MAX_LENGTH_BITS + WINDOW_SIZE_BITS > 32" +#endif + +// ----------------------------------------------------------------------------- + +static const uint8_t plane_to_code_lut[128] = { + 96, 73, 55, 39, 23, 13, 5, 1, 255, 255, 255, 255, 255, 255, 255, 255, + 101, 78, 58, 42, 26, 16, 8, 2, 0, 3, 9, 17, 27, 43, 59, 79, + 102, 86, 62, 46, 32, 20, 10, 6, 4, 7, 11, 21, 33, 47, 63, 87, + 105, 90, 70, 52, 37, 28, 18, 14, 12, 15, 19, 29, 38, 53, 71, 91, + 110, 99, 82, 66, 48, 35, 30, 24, 22, 25, 31, 36, 49, 67, 83, 100, + 115, 108, 94, 76, 64, 50, 44, 40, 34, 41, 45, 51, 65, 77, 95, 109, + 118, 113, 103, 92, 80, 68, 60, 56, 54, 57, 61, 69, 81, 93, 104, 114, + 119, 116, 111, 106, 97, 88, 84, 74, 72, 75, 85, 89, 98, 107, 112, 117 +}; + +static int DistanceToPlaneCode(int xsize, int dist) { + const int yoffset = dist / xsize; + const int xoffset = dist - yoffset * xsize; + if (xoffset <= 8 && yoffset < 8) { + return plane_to_code_lut[yoffset * 16 + 8 - xoffset] + 1; + } else if (xoffset > xsize - 8 && yoffset < 7) { + return plane_to_code_lut[(yoffset + 1) * 16 + 8 + (xsize - xoffset)] + 1; + } + return dist + 120; +} + +// Returns the exact index where array1 and array2 are different. For an index +// inferior or equal to best_len_match, the return value just has to be strictly +// inferior to best_len_match. The current behavior is to return 0 if this index +// is best_len_match, and the index itself otherwise. +// If no two elements are the same, it returns max_limit. +static WEBP_INLINE int FindMatchLength(const uint32_t* const array1, + const uint32_t* const array2, + int best_len_match, int max_limit) { + // Before 'expensive' linear match, check if the two arrays match at the + // current best length index. + if (array1[best_len_match] != array2[best_len_match]) return 0; + + return VP8LVectorMismatch(array1, array2, max_limit); +} + +// ----------------------------------------------------------------------------- +// VP8LBackwardRefs + +struct PixOrCopyBlock { + PixOrCopyBlock* next_; // next block (or NULL) + PixOrCopy* start_; // data start + int size_; // currently used size +}; + +static void ClearBackwardRefs(VP8LBackwardRefs* const refs) { + assert(refs != NULL); + if (refs->tail_ != NULL) { + *refs->tail_ = refs->free_blocks_; // recycle all blocks at once + } + refs->free_blocks_ = refs->refs_; + refs->tail_ = &refs->refs_; + refs->last_block_ = NULL; + refs->refs_ = NULL; +} + +void VP8LBackwardRefsClear(VP8LBackwardRefs* const refs) { + assert(refs != NULL); + ClearBackwardRefs(refs); + while (refs->free_blocks_ != NULL) { + PixOrCopyBlock* const next = refs->free_blocks_->next_; + WebPSafeFree(refs->free_blocks_); + refs->free_blocks_ = next; + } +} + +void VP8LBackwardRefsInit(VP8LBackwardRefs* const refs, int block_size) { + assert(refs != NULL); + memset(refs, 0, sizeof(*refs)); + refs->tail_ = &refs->refs_; + refs->block_size_ = + (block_size < MIN_BLOCK_SIZE) ? MIN_BLOCK_SIZE : block_size; +} + +VP8LRefsCursor VP8LRefsCursorInit(const VP8LBackwardRefs* const refs) { + VP8LRefsCursor c; + c.cur_block_ = refs->refs_; + if (refs->refs_ != NULL) { + c.cur_pos = c.cur_block_->start_; + c.last_pos_ = c.cur_pos + c.cur_block_->size_; + } else { + c.cur_pos = NULL; + c.last_pos_ = NULL; + } + return c; +} + +void VP8LRefsCursorNextBlock(VP8LRefsCursor* const c) { + PixOrCopyBlock* const b = c->cur_block_->next_; + c->cur_pos = (b == NULL) ? NULL : b->start_; + c->last_pos_ = (b == NULL) ? NULL : b->start_ + b->size_; + c->cur_block_ = b; +} + +// Create a new block, either from the free list or allocated +static PixOrCopyBlock* BackwardRefsNewBlock(VP8LBackwardRefs* const refs) { + PixOrCopyBlock* b = refs->free_blocks_; + if (b == NULL) { // allocate new memory chunk + const size_t total_size = + sizeof(*b) + refs->block_size_ * sizeof(*b->start_); + b = (PixOrCopyBlock*)WebPSafeMalloc(1ULL, total_size); + if (b == NULL) { + refs->error_ |= 1; + return NULL; + } + b->start_ = (PixOrCopy*)((uint8_t*)b + sizeof(*b)); // not always aligned + } else { // recycle from free-list + refs->free_blocks_ = b->next_; + } + *refs->tail_ = b; + refs->tail_ = &b->next_; + refs->last_block_ = b; + b->next_ = NULL; + b->size_ = 0; + return b; +} + +static WEBP_INLINE void BackwardRefsCursorAdd(VP8LBackwardRefs* const refs, + const PixOrCopy v) { + PixOrCopyBlock* b = refs->last_block_; + if (b == NULL || b->size_ == refs->block_size_) { + b = BackwardRefsNewBlock(refs); + if (b == NULL) return; // refs->error_ is set + } + b->start_[b->size_++] = v; +} + +int VP8LBackwardRefsCopy(const VP8LBackwardRefs* const src, + VP8LBackwardRefs* const dst) { + const PixOrCopyBlock* b = src->refs_; + ClearBackwardRefs(dst); + assert(src->block_size_ == dst->block_size_); + while (b != NULL) { + PixOrCopyBlock* const new_b = BackwardRefsNewBlock(dst); + if (new_b == NULL) return 0; // dst->error_ is set + memcpy(new_b->start_, b->start_, b->size_ * sizeof(*b->start_)); + new_b->size_ = b->size_; + b = b->next_; + } + return 1; +} + +// ----------------------------------------------------------------------------- +// Hash chains + +int VP8LHashChainInit(VP8LHashChain* const p, int size) { + assert(p->size_ == 0); + assert(p->offset_length_ == NULL); + assert(size > 0); + p->offset_length_ = + (uint32_t*)WebPSafeMalloc(size, sizeof(*p->offset_length_)); + if (p->offset_length_ == NULL) return 0; + p->size_ = size; + + return 1; +} + +void VP8LHashChainClear(VP8LHashChain* const p) { + assert(p != NULL); + WebPSafeFree(p->offset_length_); + + p->size_ = 0; + p->offset_length_ = NULL; +} + +// ----------------------------------------------------------------------------- + +#define HASH_MULTIPLIER_HI (0xc6a4a793ULL) +#define HASH_MULTIPLIER_LO (0x5bd1e996ULL) + +static WEBP_INLINE uint32_t GetPixPairHash64(const uint32_t* const argb) { + uint32_t key; + key = (argb[1] * HASH_MULTIPLIER_HI) & 0xffffffffu; + key += (argb[0] * HASH_MULTIPLIER_LO) & 0xffffffffu; + key = key >> (32 - HASH_BITS); + return key; +} + +// Returns the maximum number of hash chain lookups to do for a +// given compression quality. Return value in range [8, 86]. +static int GetMaxItersForQuality(int quality) { + return 8 + (quality * quality) / 128; +} + +static int GetWindowSizeForHashChain(int quality, int xsize) { + const int max_window_size = (quality > 75) ? WINDOW_SIZE + : (quality > 50) ? (xsize << 8) + : (quality > 25) ? (xsize << 6) + : (xsize << 4); + assert(xsize > 0); + return (max_window_size > WINDOW_SIZE) ? WINDOW_SIZE : max_window_size; +} + +static WEBP_INLINE int MaxFindCopyLength(int len) { + return (len < MAX_LENGTH) ? len : MAX_LENGTH; +} + +int VP8LHashChainFill(VP8LHashChain* const p, int quality, + const uint32_t* const argb, int xsize, int ysize, + int low_effort) { + const int size = xsize * ysize; + const int iter_max = GetMaxItersForQuality(quality); + const uint32_t window_size = GetWindowSizeForHashChain(quality, xsize); + int pos; + int argb_comp; + uint32_t base_position; + int32_t* hash_to_first_index; + // Temporarily use the p->offset_length_ as a hash chain. + int32_t* chain = (int32_t*)p->offset_length_; + assert(size > 0); + assert(p->size_ != 0); + assert(p->offset_length_ != NULL); + + if (size <= 2) { + p->offset_length_[0] = p->offset_length_[size - 1] = 0; + return 1; + } + + hash_to_first_index = + (int32_t*)WebPSafeMalloc(HASH_SIZE, sizeof(*hash_to_first_index)); + if (hash_to_first_index == NULL) return 0; + + // Set the int32_t array to -1. + memset(hash_to_first_index, 0xff, HASH_SIZE * sizeof(*hash_to_first_index)); + // Fill the chain linking pixels with the same hash. + argb_comp = (argb[0] == argb[1]); + for (pos = 0; pos < size - 2;) { + uint32_t hash_code; + const int argb_comp_next = (argb[pos + 1] == argb[pos + 2]); + if (argb_comp && argb_comp_next) { + // Consecutive pixels with the same color will share the same hash. + // We therefore use a different hash: the color and its repetition + // length. + uint32_t tmp[2]; + uint32_t len = 1; + tmp[0] = argb[pos]; + // Figure out how far the pixels are the same. + // The last pixel has a different 64 bit hash, as its next pixel does + // not have the same color, so we just need to get to the last pixel equal + // to its follower. + while (pos + (int)len + 2 < size && argb[pos + len + 2] == argb[pos]) { + ++len; + } + if (len > MAX_LENGTH) { + // Skip the pixels that match for distance=1 and length>MAX_LENGTH + // because they are linked to their predecessor and we automatically + // check that in the main for loop below. Skipping means setting no + // predecessor in the chain, hence -1. + memset(chain + pos, 0xff, (len - MAX_LENGTH) * sizeof(*chain)); + pos += len - MAX_LENGTH; + len = MAX_LENGTH; + } + // Process the rest of the hash chain. + while (len) { + tmp[1] = len--; + hash_code = GetPixPairHash64(tmp); + chain[pos] = hash_to_first_index[hash_code]; + hash_to_first_index[hash_code] = pos++; + } + argb_comp = 0; + } else { + // Just move one pixel forward. + hash_code = GetPixPairHash64(argb + pos); + chain[pos] = hash_to_first_index[hash_code]; + hash_to_first_index[hash_code] = pos++; + argb_comp = argb_comp_next; + } + } + // Process the penultimate pixel. + chain[pos] = hash_to_first_index[GetPixPairHash64(argb + pos)]; + + WebPSafeFree(hash_to_first_index); + + // Find the best match interval at each pixel, defined by an offset to the + // pixel and a length. The right-most pixel cannot match anything to the right + // (hence a best length of 0) and the left-most pixel nothing to the left + // (hence an offset of 0). + assert(size > 2); + p->offset_length_[0] = p->offset_length_[size - 1] = 0; + for (base_position = size - 2; base_position > 0;) { + const int max_len = MaxFindCopyLength(size - 1 - base_position); + const uint32_t* const argb_start = argb + base_position; + int iter = iter_max; + int best_length = 0; + uint32_t best_distance = 0; + uint32_t best_argb; + const int min_pos = + (base_position > window_size) ? base_position - window_size : 0; + const int length_max = (max_len < 256) ? max_len : 256; + uint32_t max_base_position; + + pos = chain[base_position]; + if (!low_effort) { + int curr_length; + // Heuristic: use the comparison with the above line as an initialization. + if (base_position >= (uint32_t)xsize) { + curr_length = FindMatchLength(argb_start - xsize, argb_start, + best_length, max_len); + if (curr_length > best_length) { + best_length = curr_length; + best_distance = xsize; + } + --iter; + } + // Heuristic: compare to the previous pixel. + curr_length = + FindMatchLength(argb_start - 1, argb_start, best_length, max_len); + if (curr_length > best_length) { + best_length = curr_length; + best_distance = 1; + } + --iter; + // Skip the for loop if we already have the maximum. + if (best_length == MAX_LENGTH) pos = min_pos - 1; + } + best_argb = argb_start[best_length]; + + for (; pos >= min_pos && --iter; pos = chain[pos]) { + int curr_length; + assert(base_position > (uint32_t)pos); + + if (argb[pos + best_length] != best_argb) continue; + + curr_length = VP8LVectorMismatch(argb + pos, argb_start, max_len); + if (best_length < curr_length) { + best_length = curr_length; + best_distance = base_position - pos; + best_argb = argb_start[best_length]; + // Stop if we have reached a good enough length. + if (best_length >= length_max) break; + } + } + // We have the best match but in case the two intervals continue matching + // to the left, we have the best matches for the left-extended pixels. + max_base_position = base_position; + while (1) { + assert(best_length <= MAX_LENGTH); + assert(best_distance <= WINDOW_SIZE); + p->offset_length_[base_position] = + (best_distance << MAX_LENGTH_BITS) | (uint32_t)best_length; + --base_position; + // Stop if we don't have a match or if we are out of bounds. + if (best_distance == 0 || base_position == 0) break; + // Stop if we cannot extend the matching intervals to the left. + if (base_position < best_distance || + argb[base_position - best_distance] != argb[base_position]) { + break; + } + // Stop if we are matching at its limit because there could be a closer + // matching interval with the same maximum length. Then again, if the + // matching interval is as close as possible (best_distance == 1), we will + // never find anything better so let's continue. + if (best_length == MAX_LENGTH && best_distance != 1 && + base_position + MAX_LENGTH < max_base_position) { + break; + } + if (best_length < MAX_LENGTH) { + ++best_length; + max_base_position = base_position; + } + } + } + return 1; +} + +static WEBP_INLINE int HashChainFindOffset(const VP8LHashChain* const p, + const int base_position) { + return p->offset_length_[base_position] >> MAX_LENGTH_BITS; +} + +static WEBP_INLINE int HashChainFindLength(const VP8LHashChain* const p, + const int base_position) { + return p->offset_length_[base_position] & ((1U << MAX_LENGTH_BITS) - 1); +} + +static WEBP_INLINE void HashChainFindCopy(const VP8LHashChain* const p, + int base_position, + int* const offset_ptr, + int* const length_ptr) { + *offset_ptr = HashChainFindOffset(p, base_position); + *length_ptr = HashChainFindLength(p, base_position); +} + +static WEBP_INLINE void AddSingleLiteral(uint32_t pixel, int use_color_cache, + VP8LColorCache* const hashers, + VP8LBackwardRefs* const refs) { + PixOrCopy v; + if (use_color_cache) { + const uint32_t key = VP8LColorCacheGetIndex(hashers, pixel); + if (VP8LColorCacheLookup(hashers, key) == pixel) { + v = PixOrCopyCreateCacheIdx(key); + } else { + v = PixOrCopyCreateLiteral(pixel); + VP8LColorCacheSet(hashers, key, pixel); + } + } else { + v = PixOrCopyCreateLiteral(pixel); + } + BackwardRefsCursorAdd(refs, v); +} + +static int BackwardReferencesRle(int xsize, int ysize, + const uint32_t* const argb, + int cache_bits, VP8LBackwardRefs* const refs) { + const int pix_count = xsize * ysize; + int i, k; + const int use_color_cache = (cache_bits > 0); + VP8LColorCache hashers; + + if (use_color_cache && !VP8LColorCacheInit(&hashers, cache_bits)) { + return 0; + } + ClearBackwardRefs(refs); + // Add first pixel as literal. + AddSingleLiteral(argb[0], use_color_cache, &hashers, refs); + i = 1; + while (i < pix_count) { + const int max_len = MaxFindCopyLength(pix_count - i); + const int rle_len = FindMatchLength(argb + i, argb + i - 1, 0, max_len); + const int prev_row_len = (i < xsize) ? 0 : + FindMatchLength(argb + i, argb + i - xsize, 0, max_len); + if (rle_len >= prev_row_len && rle_len >= MIN_LENGTH) { + BackwardRefsCursorAdd(refs, PixOrCopyCreateCopy(1, rle_len)); + // We don't need to update the color cache here since it is always the + // same pixel being copied, and that does not change the color cache + // state. + i += rle_len; + } else if (prev_row_len >= MIN_LENGTH) { + BackwardRefsCursorAdd(refs, PixOrCopyCreateCopy(xsize, prev_row_len)); + if (use_color_cache) { + for (k = 0; k < prev_row_len; ++k) { + VP8LColorCacheInsert(&hashers, argb[i + k]); + } + } + i += prev_row_len; + } else { + AddSingleLiteral(argb[i], use_color_cache, &hashers, refs); + i++; + } + } + if (use_color_cache) VP8LColorCacheClear(&hashers); + return !refs->error_; +} + +static int BackwardReferencesLz77(int xsize, int ysize, + const uint32_t* const argb, int cache_bits, + const VP8LHashChain* const hash_chain, + VP8LBackwardRefs* const refs) { + int i; + int i_last_check = -1; + int ok = 0; + int cc_init = 0; + const int use_color_cache = (cache_bits > 0); + const int pix_count = xsize * ysize; + VP8LColorCache hashers; + + if (use_color_cache) { + cc_init = VP8LColorCacheInit(&hashers, cache_bits); + if (!cc_init) goto Error; + } + ClearBackwardRefs(refs); + for (i = 0; i < pix_count;) { + // Alternative#1: Code the pixels starting at 'i' using backward reference. + int offset = 0; + int len = 0; + int j; + HashChainFindCopy(hash_chain, i, &offset, &len); + if (len >= MIN_LENGTH) { + const int len_ini = len; + int max_reach = 0; + assert(i + len < pix_count); + // Only start from what we have not checked already. + i_last_check = (i > i_last_check) ? i : i_last_check; + // We know the best match for the current pixel but we try to find the + // best matches for the current pixel AND the next one combined. + // The naive method would use the intervals: + // [i,i+len) + [i+len, length of best match at i+len) + // while we check if we can use: + // [i,j) (where j<=i+len) + [j, length of best match at j) + for (j = i_last_check + 1; j <= i + len_ini; ++j) { + const int len_j = HashChainFindLength(hash_chain, j); + const int reach = + j + (len_j >= MIN_LENGTH ? len_j : 1); // 1 for single literal. + if (reach > max_reach) { + len = j - i; + max_reach = reach; + } + } + } else { + len = 1; + } + // Go with literal or backward reference. + assert(len > 0); + if (len == 1) { + AddSingleLiteral(argb[i], use_color_cache, &hashers, refs); + } else { + BackwardRefsCursorAdd(refs, PixOrCopyCreateCopy(offset, len)); + if (use_color_cache) { + for (j = i; j < i + len; ++j) VP8LColorCacheInsert(&hashers, argb[j]); + } + } + i += len; + } + + ok = !refs->error_; + Error: + if (cc_init) VP8LColorCacheClear(&hashers); + return ok; +} + +// ----------------------------------------------------------------------------- + +typedef struct { + double alpha_[VALUES_IN_BYTE]; + double red_[VALUES_IN_BYTE]; + double blue_[VALUES_IN_BYTE]; + double distance_[NUM_DISTANCE_CODES]; + double* literal_; +} CostModel; + +static int BackwardReferencesTraceBackwards( + int xsize, int ysize, const uint32_t* const argb, int quality, + int cache_bits, const VP8LHashChain* const hash_chain, + VP8LBackwardRefs* const refs); + +static void ConvertPopulationCountTableToBitEstimates( + int num_symbols, const uint32_t population_counts[], double 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 double logsum = VP8LFastLog2(sum); + for (i = 0; i < num_symbols; ++i) { + output[i] = logsum - VP8LFastLog2(population_counts[i]); + } + } +} + +static int CostModelBuild(CostModel* const m, int cache_bits, + VP8LBackwardRefs* const refs) { + int ok = 0; + VP8LHistogram* const histo = VP8LAllocateHistogram(cache_bits); + if (histo == NULL) goto Error; + + VP8LHistogramCreate(histo, refs, cache_bits); + + 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 double 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 double 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 double 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 double GetDistanceCost(const CostModel* const m, + uint32_t distance) { + int code, extra_bits; + VP8LPrefixEncodeBits(distance, &code, &extra_bits); + return m->distance_[code] + extra_bits; +} + +static void AddSingleLiteralWithCostModel(const uint32_t* const argb, + VP8LColorCache* const hashers, + const CostModel* const cost_model, + int idx, int use_color_cache, + double prev_cost, float* const cost, + uint16_t* const dist_array) { + double cost_val = prev_cost; + const uint32_t color = argb[0]; + const int ix = use_color_cache ? VP8LColorCacheContains(hashers, color) : -1; + if (ix >= 0) { + // use_color_cache is true and hashers contains color + const double mul0 = 0.68; + cost_val += GetCacheCost(cost_model, ix) * mul0; + } else { + const double mul1 = 0.82; + if (use_color_cache) VP8LColorCacheInsert(hashers, color); + cost_val += GetLiteralCost(cost_model, color) * mul1; + } + if (cost[idx] > cost_val) { + cost[idx] = (float)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 100 + +// 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: +// distance_cost_ at index_ + GetLengthCost(cost_model, k) +// (named cost) (named cached cost) +// 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, for which lower_ and upper_ bounds are kept. +// 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 minimum, old intervals are split or removed. +typedef struct CostInterval CostInterval; +struct CostInterval { + double lower_; + double upper_; + int start_; + int end_; + double distance_cost_; + int index_; + CostInterval* previous_; + CostInterval* next_; +}; + +// The GetLengthCost(cost_model, k) part of the costs is also bounded for +// efficiency in a set of intervals of a different type. +// If those intervals are small enough, they are not used for comparison and +// written into the costs right away. +typedef struct { + double lower_; // Lower bound of the interval. + double upper_; // Upper bound of the interval. + int start_; + int end_; // Exclusive. + int do_write_; // If !=0, the interval is saved to cost instead of being kept + // for comparison. +} 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_; + double cost_cache_[MAX_LENGTH]; // Contains the GetLengthCost(cost_model, k). + double min_cost_cache_; // The minimum value in cost_cache_[1:]. + double max_cost_cache_; // The maximum value in cost_cache_[1:]. + 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_; + // Buffer used in BackwardReferencesHashChainDistanceOnly to store the ends + // of the intervals that can have impacted the cost at a pixel. + int* interval_ends_; + int interval_ends_size_; +} CostManager; + +static int IsCostCacheIntervalWritable(int start, int end) { + // 100 is the length for which we consider an interval for comparison, and not + // for writing. + // The first intervals are very small and go in increasing size. This constant + // helps merging them into one big interval (up to index 150/200 usually from + // which intervals start getting much bigger). + // This value is empirical. + return (end - start + 1 < 100); +} + +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_); + WebPSafeFree(manager->interval_ends_); + + // 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; + // This constant is tied to the cost_model we use. + // Empirically, differences between intervals is usually of more than 1. + const double min_cost_diff = 0.1; + + manager->costs_ = NULL; + manager->cache_intervals_ = NULL; + manager->interval_ends_ = NULL; + manager->head_ = NULL; + manager->recycled_intervals_ = NULL; + manager->count_ = 0; + manager->dist_array_ = dist_array; + CostManagerInitFreeList(manager); + + // Fill in the cost_cache_. + manager->cache_intervals_size_ = 1; + manager->cost_cache_[0] = 0; + for (i = 1; i < cost_cache_size; ++i) { + manager->cost_cache_[i] = GetLengthCost(cost_model, i); + // Get an approximation of the number of bound intervals. + if (fabs(manager->cost_cache_[i] - manager->cost_cache_[i - 1]) > + min_cost_diff) { + ++manager->cache_intervals_size_; + } + // Compute the minimum of cost_cache_. + if (i == 1) { + manager->min_cost_cache_ = manager->cost_cache_[1]; + manager->max_cost_cache_ = manager->cost_cache_[1]; + } else if (manager->cost_cache_[i] < manager->min_cost_cache_) { + manager->min_cost_cache_ = manager->cost_cache_[i]; + } else if (manager->cost_cache_[i] > manager->max_cost_cache_) { + manager->max_cost_cache_ = manager->cost_cache_[i]; + } + } + + // With the current cost models, we have 15 intervals, so we are safe by + // setting a maximum of COST_CACHE_INTERVAL_SIZE_MAX. + if (manager->cache_intervals_size_ > COST_CACHE_INTERVAL_SIZE_MAX) { + manager->cache_intervals_size_ = COST_CACHE_INTERVAL_SIZE_MAX; + } + 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_. + { + double cost_prev = -1e38f; // unprobably low initial value + CostCacheInterval* prev = NULL; + CostCacheInterval* cur = manager->cache_intervals_; + const CostCacheInterval* const end = + manager->cache_intervals_ + manager->cache_intervals_size_; + + // Consecutive values in cost_cache_ are compared and if a big enough + // difference is found, a new interval is created and bounded. + for (i = 0; i < cost_cache_size; ++i) { + const double cost_val = manager->cost_cache_[i]; + if (i == 0 || + (fabs(cost_val - cost_prev) > min_cost_diff && cur + 1 < end)) { + if (i > 1) { + const int is_writable = + IsCostCacheIntervalWritable(cur->start_, cur->end_); + // Merge with the previous interval if both are writable. + if (is_writable && cur != manager->cache_intervals_ && + prev->do_write_) { + // Update the previous interval. + prev->end_ = cur->end_; + if (cur->lower_ < prev->lower_) { + prev->lower_ = cur->lower_; + } else if (cur->upper_ > prev->upper_) { + prev->upper_ = cur->upper_; + } + } else { + cur->do_write_ = is_writable; + prev = cur; + ++cur; + } + } + // Initialize an interval. + cur->start_ = i; + cur->do_write_ = 0; + cur->lower_ = cost_val; + cur->upper_ = cost_val; + } else { + // Update the current interval bounds. + if (cost_val < cur->lower_) { + cur->lower_ = cost_val; + } else if (cost_val > cur->upper_) { + cur->upper_ = cost_val; + } + } + cur->end_ = i + 1; + cost_prev = cost_val; + } + manager->cache_intervals_size_ = cur + 1 - manager->cache_intervals_; + } + + 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] = 1e38f; + + // The cost at pixel is influenced by the cost intervals from previous pixels. + // Let us take the specific case where the offset is the same (which actually + // happens a lot in case of uniform regions). + // pixel i contributes to j>i a cost of: offset cost + cost_cache_[j-i] + // pixel i+1 contributes to j>i a cost of: 2*offset cost + cost_cache_[j-i-1] + // pixel i+2 contributes to j>i a cost of: 3*offset cost + cost_cache_[j-i-2] + // and so on. + // A pixel i influences the following length(j) < MAX_LENGTH pixels. What is + // the value of j such that pixel i + j cannot influence any of those pixels? + // This value is such that: + // max of cost_cache_ < j*offset cost + min of cost_cache_ + // (pixel i + j 's cost cannot beat the worst cost given by pixel i). + // This value will be used to optimize the cost computation in + // BackwardReferencesHashChainDistanceOnly. + { + // The offset cost is computed in GetDistanceCost and has a minimum value of + // the minimum in cost_model->distance_. The case where the offset cost is 0 + // will be dealt with differently later so we are only interested in the + // minimum non-zero offset cost. + double offset_cost_min = 0.; + int size; + for (i = 0; i < NUM_DISTANCE_CODES; ++i) { + if (cost_model->distance_[i] != 0) { + if (offset_cost_min == 0.) { + offset_cost_min = cost_model->distance_[i]; + } else if (cost_model->distance_[i] < offset_cost_min) { + offset_cost_min = cost_model->distance_[i]; + } + } + } + // In case all the cost_model->distance_ is 0, the next non-zero cost we + // can have is from the extra bit in GetDistanceCost, hence 1. + if (offset_cost_min < 1.) offset_cost_min = 1.; + + size = 1 + (int)ceil((manager->max_cost_cache_ - manager->min_cost_cache_) / + offset_cost_min); + // Empirically, we usually end up with a value below 100. + if (size > MAX_LENGTH) size = MAX_LENGTH; + + manager->interval_ends_ = + (int*)WebPSafeMalloc(size, sizeof(*manager->interval_ends_)); + if (manager->interval_ends_ == NULL) { + CostManagerClear(manager); + return 0; + } + manager->interval_ends_size_ = size; + } + + return 1; +} + +// Given the distance_cost for pixel 'index', 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 index, + double distance_cost) { + int k = i - index; + double cost_tmp; + assert(k >= 0 && k < MAX_LENGTH); + cost_tmp = distance_cost + manager->cost_cache_[k]; + + if (manager->costs_[i] > cost_tmp) { + manager->costs_[i] = (float)cost_tmp; + manager->dist_array_[i] = k + 1; + } +} + +// Given the distance_cost for pixel 'index', 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 index, + double distance_cost) { + int i; + for (i = start; i < end; ++i) UpdateCost(manager, i, index, distance_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) { + CostInterval* const next = interval->next_; + + if (interval == NULL) return; + + ConnectIntervals(manager, interval->previous_, 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. +static WEBP_INLINE void UpdateCostPerIndex(CostManager* const manager, int i) { + CostInterval* current = manager->head_; + + while (current != NULL && current->start_ <= i) { + if (current->end_ <= i) { + // We have an outdated interval, remove it. + CostInterval* next = current->next_; + PopInterval(manager, current); + current = next; + } else { + UpdateCost(manager, i, current->index_, current->distance_cost_); + current = 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, + double distance_cost, double lower, + double upper, int index, int start, + int end) { + CostInterval* interval_new; + + if (IsCostCacheIntervalWritable(start, end) || + manager->count_ >= COST_CACHE_INTERVAL_SIZE_MAX) { + // Write down the interval if it is too small. + UpdateCostPerInterval(manager, start, end, index, distance_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, index, distance_cost); + return; + } + } + + interval_new->distance_cost_ = distance_cost; + interval_new->lower_ = lower; + interval_new->upper_ = upper; + interval_new->index_ = index; + interval_new->start_ = start; + interval_new->end_ = end; + PositionOrphanInterval(manager, interval_new, interval_in); + + ++manager->count_; +} + +// When an interval has its start_ or end_ modified, it needs to be +// repositioned in the linked list. +static WEBP_INLINE void RepositionInterval(CostManager* const manager, + CostInterval* const interval) { + if (IsCostCacheIntervalWritable(interval->start_, interval->end_)) { + // Maybe interval has been resized and is small enough to be removed. + UpdateCostPerInterval(manager, interval->start_, interval->end_, + interval->index_, interval->distance_cost_); + PopInterval(manager, interval); + return; + } + + // Early exit if interval is at the right spot. + if ((interval->previous_ == NULL || + interval->previous_->start_ <= interval->start_) && + (interval->next_ == NULL || + interval->start_ <= interval->next_->start_)) { + return; + } + + ConnectIntervals(manager, interval->previous_, interval->next_); + PositionOrphanInterval(manager, interval, interval->previous_); +} + +// Given a new cost interval defined by its start at index, its last 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, + double distance_cost, int index, + int last) { + size_t i; + CostInterval* interval = manager->head_; + CostInterval* interval_next; + const CostCacheInterval* const cost_cache_intervals = + manager->cache_intervals_; + + for (i = 0; i < manager->cache_intervals_size_ && + cost_cache_intervals[i].start_ < last; + ++i) { + // Define the intersection of the ith interval with the new one. + int start = index + cost_cache_intervals[i].start_; + const int end = index + (cost_cache_intervals[i].end_ > last + ? last + : cost_cache_intervals[i].end_); + const double lower_in = cost_cache_intervals[i].lower_; + const double upper_in = cost_cache_intervals[i].upper_; + const double lower_full_in = distance_cost + lower_in; + const double upper_full_in = distance_cost + upper_in; + + if (cost_cache_intervals[i].do_write_) { + UpdateCostPerInterval(manager, start, end, index, distance_cost); + continue; + } + + for (; interval != NULL && interval->start_ < end && start < end; + interval = interval_next) { + const double lower_full_interval = + interval->distance_cost_ + interval->lower_; + const double upper_full_interval = + interval->distance_cost_ + interval->upper_; + + interval_next = interval->next_; + + // Make sure we have some overlap + if (start >= interval->end_) continue; + + if (lower_full_in >= upper_full_interval) { + // 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, distance_cost, lower_in, upper_in, + index, start, interval->start_); + start = start_new; + continue; + } + + // We know the two intervals intersect. + if (upper_full_in >= lower_full_interval) { + // There is no clear cut on which is best, so let's keep both. + // [*********[*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*]***********] + // start interval->start_ interval->end_ end + // OR + // [*********[*-*-*-*-*-*-*-*-*-*-*-]----------------------] + // start interval->start_ end interval->end_ + const int end_new = (interval->end_ <= end) ? interval->end_ : end; + InsertInterval(manager, interval, distance_cost, lower_in, upper_in, + index, start, end_new); + start = end_new; + } else if (start <= interval->start_ && 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 { + if (interval->start_ <= start && 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->distance_cost_, + interval->lower_, interval->upper_, interval->index_, + end, end_original); + } else if (interval->start_ < start) { + // [------------------------------------] + // interval->start_ interval->end_ + // [*****************************] + // start end + interval->end_ = start; + } else { + // [------------------------------------] + // interval->start_ interval->end_ + // [*****************************] + // start end + interval->start_ = end; + } + + // The interval has been modified, we need to reposition it or write it. + RepositionInterval(manager, interval); + } + } + // Insert the remaining interval from start to end. + InsertInterval(manager, interval, distance_cost, lower_in, upper_in, index, + start, end); + } +} + +static int BackwardReferencesHashChainDistanceOnly( + int xsize, int ysize, const uint32_t* const argb, int quality, + int cache_bits, const VP8LHashChain* const hash_chain, + 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(double) * + (NUM_LITERAL_CODES + NUM_LENGTH_CODES + + ((cache_bits > 0) ? (1 << cache_bits) : 0)); + const size_t cost_model_size = sizeof(CostModel) + literal_array_size; + CostModel* const cost_model = + (CostModel*)WebPSafeCalloc(1ULL, cost_model_size); + VP8LColorCache hashers; + const int skip_length = 32 + quality; + const int skip_min_distance_code = 2; + CostManager* cost_manager = + (CostManager*)WebPSafeMalloc(1ULL, sizeof(*cost_manager)); + + if (cost_model == NULL || cost_manager == NULL) goto Error; + + cost_model->literal_ = (double*)(cost_model + 1); + if (use_color_cache) { + cc_init = VP8LColorCacheInit(&hashers, cache_bits); + if (!cc_init) goto Error; + } + + if (!CostModelBuild(cost_model, 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 + 0, &hashers, cost_model, 0, + use_color_cache, 0.0, cost_manager->costs_, + dist_array); + + for (i = 1; i < pix_count - 1; ++i) { + int offset = 0, len = 0; + double prev_cost = cost_manager->costs_[i - 1]; + HashChainFindCopy(hash_chain, i, &offset, &len); + if (len >= 2) { + // If we are dealing with a non-literal. + const int code = DistanceToPlaneCode(xsize, offset); + const double offset_cost = GetDistanceCost(cost_model, code); + const int first_i = i; + int j_max = 0, interval_ends_index = 0; + const int is_offset_zero = (offset_cost == 0.); + + if (!is_offset_zero) { + j_max = (int)ceil( + (cost_manager->max_cost_cache_ - cost_manager->min_cost_cache_) / + offset_cost); + if (j_max < 1) { + j_max = 1; + } else if (j_max > cost_manager->interval_ends_size_ - 1) { + // This could only happen in the case of MAX_LENGTH. + j_max = cost_manager->interval_ends_size_ - 1; + } + } // else j_max is unused anyway. + + // 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). + for (; i < pix_count - 1; ++i) { + int offset_next, len_next; + prev_cost = cost_manager->costs_[i - 1]; + + if (is_offset_zero) { + // No optimization can be made so we just push all of the + // contributions from i. + PushInterval(cost_manager, prev_cost, i, len); + } else { + // j_max is chosen as the smallest j such that: + // max of cost_cache_ < j*offset cost + min of cost_cache_ + // Therefore, the pixel influenced by i-j_max, cannot be influenced + // by i. Only the costs after the end of what i contributed need to be + // updated. cost_manager->interval_ends_ is a circular buffer that + // stores those ends. + const double distance_cost = prev_cost + offset_cost; + int j = cost_manager->interval_ends_[interval_ends_index]; + if (i - first_i <= j_max || + !IsCostCacheIntervalWritable(j, i + len)) { + PushInterval(cost_manager, distance_cost, i, len); + } else { + for (; j < i + len; ++j) { + UpdateCost(cost_manager, j, i, distance_cost); + } + } + // Store the new end in the circular buffer. + assert(interval_ends_index < cost_manager->interval_ends_size_); + cost_manager->interval_ends_[interval_ends_index] = i + len; + if (++interval_ends_index > j_max) interval_ends_index = 0; + } + + // Check whether i is the last pixel to consider, as it is handled + // differently. + if (i + 1 >= pix_count - 1) break; + HashChainFindCopy(hash_chain, i + 1, &offset_next, &len_next); + if (offset_next != offset) break; + len = len_next; + UpdateCostPerIndex(cost_manager, i); + AddSingleLiteralWithCostModel(argb + i, &hashers, cost_model, i, + use_color_cache, prev_cost, + cost_manager->costs_, dist_array); + } + // Submit the last pixel. + UpdateCostPerIndex(cost_manager, i + 1); + + // This if is for speedup only. It roughly doubles the speed, and + // makes compression worse by .1 %. + if (len >= skip_length && code <= skip_min_distance_code) { + // Long copy for short distances, let's skip the middle + // lookups for better copies. + // 1) insert the hashes. + if (use_color_cache) { + int k; + for (k = 0; k < len; ++k) { + VP8LColorCacheInsert(&hashers, argb[i + k]); + } + } + // 2) jump. + { + const int i_next = i + len - 1; // for loop does ++i, thus -1 here. + for (; i <= i_next; ++i) UpdateCostPerIndex(cost_manager, i + 1); + i = i_next; + } + goto next_symbol; + } + if (len > 2) { + // Also try the smallest interval possible (size 2). + double cost_total = + prev_cost + offset_cost + GetLengthCost(cost_model, 1); + if (cost_manager->costs_[i + 1] > cost_total) { + cost_manager->costs_[i + 1] = (float)cost_total; + dist_array[i + 1] = 2; + } + } + } else { + // The pixel is added as a single literal so just update the costs. + UpdateCostPerIndex(cost_manager, i + 1); + } + + AddSingleLiteralWithCostModel(argb + i, &hashers, cost_model, i, + use_color_cache, prev_cost, + cost_manager->costs_, dist_array); + + next_symbol: ; + } + // Handle the last pixel. + if (i == (pix_count - 1)) { + AddSingleLiteralWithCostModel( + argb + i, &hashers, cost_model, i, use_color_cache, + cost_manager->costs_[pix_count - 2], cost_manager->costs_, dist_array); + } + + 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; + } + + ClearBackwardRefs(refs); + for (ix = 0; ix < chosen_path_size; ++ix) { + const int len = chosen_path[ix]; + if (len != 1) { + int k; + const int offset = HashChainFindOffset(hash_chain, i); + BackwardRefsCursorAdd(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]); + } + BackwardRefsCursorAdd(refs, v); + ++i; + } + } + ok = !refs->error_; + Error: + if (cc_init) VP8LColorCacheClear(&hashers); + return ok; +} + +// Returns 1 on success. +static int BackwardReferencesTraceBackwards( + int xsize, int ysize, const uint32_t* const argb, int quality, + int cache_bits, const VP8LHashChain* const hash_chain, + VP8LBackwardRefs* const refs) { + 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, quality, cache_bits, hash_chain, + refs, 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)) { + goto Error; + } + ok = 1; + Error: + WebPSafeFree(dist_array); + return ok; +} + +static void BackwardReferences2DLocality(int xsize, + const VP8LBackwardRefs* const refs) { + VP8LRefsCursor c = VP8LRefsCursorInit(refs); + while (VP8LRefsCursorOk(&c)) { + if (PixOrCopyIsCopy(c.cur_pos)) { + const int dist = c.cur_pos->argb_or_distance; + const int transformed_dist = DistanceToPlaneCode(xsize, dist); + c.cur_pos->argb_or_distance = transformed_dist; + } + VP8LRefsCursorNext(&c); + } +} + +// Computes the entropies for a color cache size (in bits) between 0 (unused) +// and cache_bits_max (inclusive). +// Returns 1 on success, 0 in case of allocation error. +static int ComputeCacheEntropies(const uint32_t* argb, + const VP8LBackwardRefs* const refs, + int cache_bits_max, double entropies[]) { + int cc_init[MAX_COLOR_CACHE_BITS + 1] = { 0 }; + VP8LColorCache hashers[MAX_COLOR_CACHE_BITS + 1]; + VP8LRefsCursor c = VP8LRefsCursorInit(refs); + VP8LHistogram* histos[MAX_COLOR_CACHE_BITS + 1] = { NULL }; + int ok = 0; + int i; + + for (i = 0; i <= cache_bits_max; ++i) { + histos[i] = VP8LAllocateHistogram(i); + if (histos[i] == NULL) goto Error; + if (i == 0) continue; + cc_init[i] = VP8LColorCacheInit(&hashers[i], i); + if (!cc_init[i]) goto Error; + } + + assert(cache_bits_max >= 0); + // Do not use the color cache for cache_bits=0. + while (VP8LRefsCursorOk(&c)) { + VP8LHistogramAddSinglePixOrCopy(histos[0], c.cur_pos); + VP8LRefsCursorNext(&c); + } + if (cache_bits_max > 0) { + c = VP8LRefsCursorInit(refs); + while (VP8LRefsCursorOk(&c)) { + const PixOrCopy* const v = c.cur_pos; + if (PixOrCopyIsLiteral(v)) { + const uint32_t pix = *argb++; + // The keys of the caches can be derived from the longest one. + int key = HashPix(pix, 32 - cache_bits_max); + for (i = cache_bits_max; i >= 1; --i, key >>= 1) { + if (VP8LColorCacheLookup(&hashers[i], key) == pix) { + ++histos[i]->literal_[NUM_LITERAL_CODES + NUM_LENGTH_CODES + key]; + } else { + VP8LColorCacheSet(&hashers[i], key, pix); + ++histos[i]->blue_[pix & 0xff]; + ++histos[i]->literal_[(pix >> 8) & 0xff]; + ++histos[i]->red_[(pix >> 16) & 0xff]; + ++histos[i]->alpha_[pix >> 24]; + } + } + } else { + // Update the histograms for distance/length. + int len = PixOrCopyLength(v); + int code_dist, code_len, extra_bits; + uint32_t argb_prev = *argb ^ 0xffffffffu; + VP8LPrefixEncodeBits(len, &code_len, &extra_bits); + VP8LPrefixEncodeBits(PixOrCopyDistance(v), &code_dist, &extra_bits); + for (i = 1; i <= cache_bits_max; ++i) { + ++histos[i]->literal_[NUM_LITERAL_CODES + code_len]; + ++histos[i]->distance_[code_dist]; + } + // Update the colors caches. + do { + if (*argb != argb_prev) { + // Efficiency: insert only if the color changes. + int key = HashPix(*argb, 32 - cache_bits_max); + for (i = cache_bits_max; i >= 1; --i, key >>= 1) { + hashers[i].colors_[key] = *argb; + } + argb_prev = *argb; + } + argb++; + } while (--len != 0); + } + VP8LRefsCursorNext(&c); + } + } + for (i = 0; i <= cache_bits_max; ++i) { + entropies[i] = VP8LHistogramEstimateBits(histos[i]); + } + ok = 1; +Error: + for (i = 0; i <= cache_bits_max; ++i) { + if (cc_init[i]) VP8LColorCacheClear(&hashers[i]); + VP8LFreeHistogram(histos[i]); + } + return ok; +} + +// Evaluate optimal cache bits for the local color cache. +// The input *best_cache_bits sets the maximum cache bits to use (passing 0 +// implies disabling the local color cache). The local color cache is also +// disabled for the lower (<= 25) quality. +// Returns 0 in case of memory error. +static int CalculateBestCacheSize(const uint32_t* const argb, + int xsize, int ysize, int quality, + const VP8LHashChain* const hash_chain, + VP8LBackwardRefs* const refs, + int* const lz77_computed, + int* const best_cache_bits) { + int i; + int cache_bits_high = (quality <= 25) ? 0 : *best_cache_bits; + double entropy_min = MAX_ENTROPY; + double entropies[MAX_COLOR_CACHE_BITS + 1]; + + assert(cache_bits_high <= MAX_COLOR_CACHE_BITS); + + *lz77_computed = 0; + if (cache_bits_high == 0) { + *best_cache_bits = 0; + // Local color cache is disabled. + return 1; + } + // Compute LZ77 with no cache (0 bits), as the ideal LZ77 with a color cache + // is not that different in practice. + if (!BackwardReferencesLz77(xsize, ysize, argb, 0, hash_chain, refs)) { + return 0; + } + // Find the cache_bits giving the lowest entropy. The search is done in a + // brute-force way as the function (entropy w.r.t cache_bits) can be + // anything in practice. + if (!ComputeCacheEntropies(argb, refs, cache_bits_high, entropies)) { + return 0; + } + for (i = 0; i <= cache_bits_high; ++i) { + if (i == 0 || entropies[i] < entropy_min) { + entropy_min = entropies[i]; + *best_cache_bits = i; + } + } + return 1; +} + +// Update (in-place) backward references for specified cache_bits. +static int BackwardRefsWithLocalCache(const uint32_t* const argb, + int cache_bits, + VP8LBackwardRefs* const refs) { + int pixel_index = 0; + VP8LColorCache hashers; + VP8LRefsCursor c = VP8LRefsCursorInit(refs); + if (!VP8LColorCacheInit(&hashers, cache_bits)) return 0; + + while (VP8LRefsCursorOk(&c)) { + PixOrCopy* const v = c.cur_pos; + if (PixOrCopyIsLiteral(v)) { + const uint32_t argb_literal = v->argb_or_distance; + const int ix = VP8LColorCacheContains(&hashers, argb_literal); + if (ix >= 0) { + // hashers contains argb_literal + *v = PixOrCopyCreateCacheIdx(ix); + } else { + VP8LColorCacheInsert(&hashers, argb_literal); + } + ++pixel_index; + } else { + // refs was created without local cache, so it can not have cache indexes. + int k; + assert(PixOrCopyIsCopy(v)); + for (k = 0; k < v->len; ++k) { + VP8LColorCacheInsert(&hashers, argb[pixel_index++]); + } + } + VP8LRefsCursorNext(&c); + } + VP8LColorCacheClear(&hashers); + return 1; +} + +static VP8LBackwardRefs* GetBackwardReferencesLowEffort( + int width, int height, const uint32_t* const argb, + int* const cache_bits, const VP8LHashChain* const hash_chain, + VP8LBackwardRefs refs_array[2]) { + VP8LBackwardRefs* refs_lz77 = &refs_array[0]; + *cache_bits = 0; + if (!BackwardReferencesLz77(width, height, argb, 0, hash_chain, refs_lz77)) { + return NULL; + } + BackwardReferences2DLocality(width, refs_lz77); + return refs_lz77; +} + +static VP8LBackwardRefs* GetBackwardReferences( + int width, int height, const uint32_t* const argb, int quality, + int* const cache_bits, const VP8LHashChain* const hash_chain, + VP8LBackwardRefs refs_array[2]) { + int lz77_is_useful; + int lz77_computed; + double bit_cost_lz77, bit_cost_rle; + VP8LBackwardRefs* best = NULL; + VP8LBackwardRefs* refs_lz77 = &refs_array[0]; + VP8LBackwardRefs* refs_rle = &refs_array[1]; + VP8LHistogram* histo = NULL; + + if (!CalculateBestCacheSize(argb, width, height, quality, hash_chain, + refs_lz77, &lz77_computed, cache_bits)) { + goto Error; + } + + if (lz77_computed) { + // Transform refs_lz77 for the optimized cache_bits. + if (*cache_bits > 0) { + if (!BackwardRefsWithLocalCache(argb, *cache_bits, refs_lz77)) { + goto Error; + } + } + } else { + if (!BackwardReferencesLz77(width, height, argb, *cache_bits, hash_chain, + refs_lz77)) { + goto Error; + } + } + + if (!BackwardReferencesRle(width, height, argb, *cache_bits, refs_rle)) { + goto Error; + } + + histo = VP8LAllocateHistogram(*cache_bits); + if (histo == NULL) goto Error; + + { + // Evaluate LZ77 coding. + VP8LHistogramCreate(histo, refs_lz77, *cache_bits); + bit_cost_lz77 = VP8LHistogramEstimateBits(histo); + // Evaluate RLE coding. + VP8LHistogramCreate(histo, refs_rle, *cache_bits); + bit_cost_rle = VP8LHistogramEstimateBits(histo); + // Decide if LZ77 is useful. + lz77_is_useful = (bit_cost_lz77 < bit_cost_rle); + } + + // Choose appropriate backward reference. + if (lz77_is_useful) { + // TraceBackwards is costly. Don't execute it at lower quality. + const int try_lz77_trace_backwards = (quality >= 25); + best = refs_lz77; // default guess: lz77 is better + if (try_lz77_trace_backwards) { + VP8LBackwardRefs* const refs_trace = refs_rle; + if (!VP8LBackwardRefsCopy(refs_lz77, refs_trace)) { + best = NULL; + goto Error; + } + if (BackwardReferencesTraceBackwards(width, height, argb, quality, + *cache_bits, hash_chain, + refs_trace)) { + double bit_cost_trace; + // Evaluate LZ77 coding. + VP8LHistogramCreate(histo, refs_trace, *cache_bits); + bit_cost_trace = VP8LHistogramEstimateBits(histo); + if (bit_cost_trace < bit_cost_lz77) { + best = refs_trace; + } + } + } + } else { + best = refs_rle; + } + + BackwardReferences2DLocality(width, best); + + Error: + VP8LFreeHistogram(histo); + return best; +} + +VP8LBackwardRefs* VP8LGetBackwardReferences( + int width, int height, const uint32_t* const argb, int quality, + int low_effort, int* const cache_bits, + const VP8LHashChain* const hash_chain, VP8LBackwardRefs refs_array[2]) { + if (low_effort) { + return GetBackwardReferencesLowEffort(width, height, argb, cache_bits, + hash_chain, refs_array); + } else { + return GetBackwardReferences(width, height, argb, quality, cache_bits, + hash_chain, refs_array); + } +} |