| // 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 <stdio.h> |
| |
| #include "./backward_references.h" |
| #include "./histogram.h" |
| #include "../dsp/lossless.h" |
| #include "../utils/color_cache.h" |
| #include "../utils/utils.h" |
| |
| #define VALUES_IN_BYTE 256 |
| |
| #define HASH_BITS 18 |
| #define HASH_SIZE (1 << HASH_BITS) |
| #define HASH_MULTIPLIER (0xc6a4a7935bd1e995ULL) |
| |
| // 1M window (4M bytes) minus 120 special codes for short distances. |
| #define WINDOW_SIZE ((1 << 20) - 120) |
| |
| // Bounds for the match length. |
| #define MIN_LENGTH 2 |
| #define MAX_LENGTH 4096 |
| |
| typedef struct { |
| // Stores the most recently added position with the given hash value. |
| int32_t hash_to_first_index_[HASH_SIZE]; |
| // chain_[pos] stores the previous position with the same hash value |
| // for every pixel in the image. |
| int32_t* chain_; |
| } HashChain; |
| |
| // ----------------------------------------------------------------------------- |
| |
| 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; |
| } |
| |
| static WEBP_INLINE int FindMatchLength(const uint32_t* const array1, |
| const uint32_t* const array2, |
| const int max_limit) { |
| int match_len = 0; |
| while (match_len < max_limit && array1[match_len] == array2[match_len]) { |
| ++match_len; |
| } |
| return match_len; |
| } |
| |
| // ----------------------------------------------------------------------------- |
| // VP8LBackwardRefs |
| |
| void VP8LInitBackwardRefs(VP8LBackwardRefs* const refs) { |
| if (refs != NULL) { |
| refs->refs = NULL; |
| refs->size = 0; |
| refs->max_size = 0; |
| } |
| } |
| |
| void VP8LClearBackwardRefs(VP8LBackwardRefs* const refs) { |
| if (refs != NULL) { |
| free(refs->refs); |
| VP8LInitBackwardRefs(refs); |
| } |
| } |
| |
| int VP8LBackwardRefsAlloc(VP8LBackwardRefs* const refs, int max_size) { |
| assert(refs != NULL); |
| refs->size = 0; |
| refs->max_size = 0; |
| refs->refs = (PixOrCopy*)WebPSafeMalloc((uint64_t)max_size, |
| sizeof(*refs->refs)); |
| if (refs->refs == NULL) return 0; |
| refs->max_size = max_size; |
| return 1; |
| } |
| |
| // ----------------------------------------------------------------------------- |
| // Hash chains |
| |
| static WEBP_INLINE uint64_t GetPixPairHash64(const uint32_t* const argb) { |
| uint64_t key = ((uint64_t)(argb[1]) << 32) | argb[0]; |
| key = (key * HASH_MULTIPLIER) >> (64 - HASH_BITS); |
| return key; |
| } |
| |
| static int HashChainInit(HashChain* const p, int size) { |
| int i; |
| p->chain_ = (int*)WebPSafeMalloc((uint64_t)size, sizeof(*p->chain_)); |
| if (p->chain_ == NULL) { |
| return 0; |
| } |
| for (i = 0; i < size; ++i) { |
| p->chain_[i] = -1; |
| } |
| for (i = 0; i < HASH_SIZE; ++i) { |
| p->hash_to_first_index_[i] = -1; |
| } |
| return 1; |
| } |
| |
| static void HashChainDelete(HashChain* const p) { |
| if (p != NULL) { |
| free(p->chain_); |
| free(p); |
| } |
| } |
| |
| // Insertion of two pixels at a time. |
| static void HashChainInsert(HashChain* const p, |
| const uint32_t* const argb, int pos) { |
| const uint64_t hash_code = GetPixPairHash64(argb); |
| p->chain_[pos] = p->hash_to_first_index_[hash_code]; |
| p->hash_to_first_index_[hash_code] = pos; |
| } |
| |
| static void GetParamsForHashChainFindCopy(int quality, int xsize, |
| int cache_bits, int* window_size, |
| int* iter_pos, int* iter_limit) { |
| const int iter_mult = (quality < 27) ? 1 : 1 + ((quality - 27) >> 4); |
| const int iter_neg = -iter_mult * (quality >> 1); |
| // Limit the backward-ref window size for lower qualities. |
| const int max_window_size = (quality > 50) ? WINDOW_SIZE |
| : (quality > 25) ? (xsize << 8) |
| : (xsize << 4); |
| assert(xsize > 0); |
| *window_size = (max_window_size > WINDOW_SIZE) ? WINDOW_SIZE |
| : max_window_size; |
| *iter_pos = 8 + (quality >> 3); |
| // For lower entropy images, the rigourous search loop in HashChainFindCopy |
| // can be relaxed. |
| *iter_limit = (cache_bits > 0) ? iter_neg : iter_neg / 2; |
| } |
| |
| static int HashChainFindCopy(const HashChain* const p, |
| int base_position, int xsize_signed, |
| const uint32_t* const argb, int maxlen, |
| int window_size, int iter_pos, int iter_limit, |
| int* const distance_ptr, |
| int* const length_ptr) { |
| const uint32_t* const argb_start = argb + base_position; |
| uint64_t best_val = 0; |
| uint32_t best_length = 1; |
| uint32_t best_distance = 0; |
| const uint32_t xsize = (uint32_t)xsize_signed; |
| const int min_pos = |
| (base_position > window_size) ? base_position - window_size : 0; |
| int pos; |
| assert(xsize > 0); |
| for (pos = p->hash_to_first_index_[GetPixPairHash64(argb_start)]; |
| pos >= min_pos; |
| pos = p->chain_[pos]) { |
| uint64_t val; |
| uint32_t curr_length; |
| uint32_t distance; |
| if (iter_pos < 0) { |
| if (iter_pos < iter_limit || best_val >= 0xff0000) { |
| break; |
| } |
| } |
| --iter_pos; |
| if (argb[pos + best_length - 1] != argb_start[best_length - 1]) { |
| continue; |
| } |
| curr_length = FindMatchLength(argb + pos, argb_start, maxlen); |
| if (curr_length < best_length) { |
| continue; |
| } |
| distance = (uint32_t)(base_position - pos); |
| val = curr_length << 16; |
| // Favoring 2d locality here gives savings for certain images. |
| if (distance < 9 * xsize) { |
| const uint32_t y = distance / xsize; |
| uint32_t x = distance % xsize; |
| if (x > (xsize >> 1)) { |
| x = xsize - x; |
| } |
| if (x <= 7) { |
| val += 9 * 9 + 9 * 9; |
| val -= y * y + x * x; |
| } |
| } |
| if (best_val < val) { |
| best_val = val; |
| best_length = curr_length; |
| best_distance = distance; |
| if (curr_length >= MAX_LENGTH) { |
| break; |
| } |
| if ((best_distance == 1 || distance == xsize) && |
| best_length >= 128) { |
| break; |
| } |
| } |
| } |
| *distance_ptr = (int)best_distance; |
| *length_ptr = best_length; |
| return (best_length >= MIN_LENGTH); |
| } |
| |
| static WEBP_INLINE void PushBackCopy(VP8LBackwardRefs* const refs, int length) { |
| int size = refs->size; |
| while (length >= MAX_LENGTH) { |
| refs->refs[size++] = PixOrCopyCreateCopy(1, MAX_LENGTH); |
| length -= MAX_LENGTH; |
| } |
| if (length > 0) { |
| refs->refs[size++] = PixOrCopyCreateCopy(1, length); |
| } |
| refs->size = size; |
| } |
| |
| static void BackwardReferencesRle(int xsize, int ysize, |
| const uint32_t* const argb, |
| VP8LBackwardRefs* const refs) { |
| const int pix_count = xsize * ysize; |
| int match_len = 0; |
| int i; |
| refs->size = 0; |
| PushBackCopy(refs, match_len); // i=0 case |
| refs->refs[refs->size++] = PixOrCopyCreateLiteral(argb[0]); |
| for (i = 1; i < pix_count; ++i) { |
| if (argb[i] == argb[i - 1]) { |
| ++match_len; |
| } else { |
| PushBackCopy(refs, match_len); |
| match_len = 0; |
| refs->refs[refs->size++] = PixOrCopyCreateLiteral(argb[i]); |
| } |
| } |
| PushBackCopy(refs, match_len); |
| } |
| |
| static int BackwardReferencesHashChain(int xsize, int ysize, |
| const uint32_t* const argb, |
| int cache_bits, int quality, |
| VP8LBackwardRefs* const refs) { |
| int i; |
| int ok = 0; |
| int cc_init = 0; |
| const int use_color_cache = (cache_bits > 0); |
| const int pix_count = xsize * ysize; |
| HashChain* const hash_chain = (HashChain*)malloc(sizeof(*hash_chain)); |
| VP8LColorCache hashers; |
| int window_size = WINDOW_SIZE; |
| int iter_pos = 1; |
| int iter_limit = -1; |
| |
| if (hash_chain == NULL) return 0; |
| if (use_color_cache) { |
| cc_init = VP8LColorCacheInit(&hashers, cache_bits); |
| if (!cc_init) goto Error; |
| } |
| |
| if (!HashChainInit(hash_chain, pix_count)) goto Error; |
| |
| refs->size = 0; |
| GetParamsForHashChainFindCopy(quality, xsize, cache_bits, |
| &window_size, &iter_pos, &iter_limit); |
| for (i = 0; i < pix_count; ) { |
| // Alternative#1: Code the pixels starting at 'i' using backward reference. |
| int offset = 0; |
| int len = 0; |
| if (i < pix_count - 1) { // FindCopy(i,..) reads pixels at [i] and [i + 1]. |
| int maxlen = pix_count - i; |
| if (maxlen > MAX_LENGTH) { |
| maxlen = MAX_LENGTH; |
| } |
| HashChainFindCopy(hash_chain, i, xsize, argb, maxlen, |
| window_size, iter_pos, iter_limit, |
| &offset, &len); |
| } |
| if (len >= MIN_LENGTH) { |
| // Alternative#2: Insert the pixel at 'i' as literal, and code the |
| // pixels starting at 'i + 1' using backward reference. |
| int offset2 = 0; |
| int len2 = 0; |
| int k; |
| HashChainInsert(hash_chain, &argb[i], i); |
| if (i < pix_count - 2) { // FindCopy(i+1,..) reads [i + 1] and [i + 2]. |
| int maxlen = pix_count - (i + 1); |
| if (maxlen > MAX_LENGTH) { |
| maxlen = MAX_LENGTH; |
| } |
| HashChainFindCopy(hash_chain, i + 1, xsize, argb, maxlen, |
| window_size, iter_pos, iter_limit, |
| &offset2, &len2); |
| if (len2 > len + 1) { |
| const uint32_t pixel = argb[i]; |
| // Alternative#2 is a better match. So push pixel at 'i' as literal. |
| if (use_color_cache && VP8LColorCacheContains(&hashers, pixel)) { |
| const int ix = VP8LColorCacheGetIndex(&hashers, pixel); |
| refs->refs[refs->size] = PixOrCopyCreateCacheIdx(ix); |
| } else { |
| refs->refs[refs->size] = PixOrCopyCreateLiteral(pixel); |
| } |
| ++refs->size; |
| if (use_color_cache) VP8LColorCacheInsert(&hashers, pixel); |
| i++; // Backward reference to be done for next pixel. |
| len = len2; |
| offset = offset2; |
| } |
| } |
| if (len >= MAX_LENGTH) { |
| len = MAX_LENGTH - 1; |
| } |
| refs->refs[refs->size++] = PixOrCopyCreateCopy(offset, len); |
| if (use_color_cache) { |
| for (k = 0; k < len; ++k) { |
| VP8LColorCacheInsert(&hashers, argb[i + k]); |
| } |
| } |
| // Add to the hash_chain (but cannot add the last pixel). |
| { |
| const int last = (len < pix_count - 1 - i) ? len : pix_count - 1 - i; |
| for (k = 1; k < last; ++k) { |
| HashChainInsert(hash_chain, &argb[i + k], i + k); |
| } |
| } |
| i += len; |
| } else { |
| const uint32_t pixel = argb[i]; |
| if (use_color_cache && VP8LColorCacheContains(&hashers, pixel)) { |
| // push pixel as a PixOrCopyCreateCacheIdx pixel |
| const int ix = VP8LColorCacheGetIndex(&hashers, pixel); |
| refs->refs[refs->size] = PixOrCopyCreateCacheIdx(ix); |
| } else { |
| refs->refs[refs->size] = PixOrCopyCreateLiteral(pixel); |
| } |
| ++refs->size; |
| if (use_color_cache) VP8LColorCacheInsert(&hashers, pixel); |
| if (i + 1 < pix_count) { |
| HashChainInsert(hash_chain, &argb[i], i); |
| } |
| ++i; |
| } |
| } |
| ok = 1; |
| Error: |
| if (cc_init) VP8LColorCacheClear(&hashers); |
| HashChainDelete(hash_chain); |
| return ok; |
| } |
| |
| // ----------------------------------------------------------------------------- |
| |
| typedef struct { |
| double alpha_[VALUES_IN_BYTE]; |
| double red_[VALUES_IN_BYTE]; |
| double literal_[PIX_OR_COPY_CODES_MAX]; |
| double blue_[VALUES_IN_BYTE]; |
| double distance_[NUM_DISTANCE_CODES]; |
| } CostModel; |
| |
| static int BackwardReferencesTraceBackwards( |
| int xsize, int ysize, int recursive_cost_model, |
| const uint32_t* const argb, int quality, int cache_bits, |
| VP8LBackwardRefs* const refs); |
| |
| static void ConvertPopulationCountTableToBitEstimates( |
| int num_symbols, const int population_counts[], double output[]) { |
| int 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 xsize, int ysize, |
| int recursion_level, const uint32_t* const argb, |
| int quality, int cache_bits) { |
| int ok = 0; |
| VP8LHistogram histo; |
| VP8LBackwardRefs refs; |
| |
| if (!VP8LBackwardRefsAlloc(&refs, xsize * ysize)) goto Error; |
| |
| if (recursion_level > 0) { |
| if (!BackwardReferencesTraceBackwards(xsize, ysize, recursion_level - 1, |
| argb, quality, cache_bits, &refs)) { |
| goto Error; |
| } |
| } else { |
| if (!BackwardReferencesHashChain(xsize, ysize, argb, cache_bits, quality, |
| &refs)) { |
| goto Error; |
| } |
| } |
| VP8LHistogramCreate(&histo, &refs, cache_bits); |
| ConvertPopulationCountTableToBitEstimates( |
| VP8LHistogramNumCodes(&histo), 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: |
| VP8LClearBackwardRefs(&refs); |
| 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_count, extra_bits_value; |
| PrefixEncode(length, &code, &extra_bits_count, &extra_bits_value); |
| return m->literal_[VALUES_IN_BYTE + code] + extra_bits_count; |
| } |
| |
| static WEBP_INLINE double GetDistanceCost(const CostModel* const m, |
| uint32_t distance) { |
| int code, extra_bits_count, extra_bits_value; |
| PrefixEncode(distance, &code, &extra_bits_count, &extra_bits_value); |
| return m->distance_[code] + extra_bits_count; |
| } |
| |
| static int BackwardReferencesHashChainDistanceOnly( |
| int xsize, int ysize, int recursive_cost_model, const uint32_t* const argb, |
| int quality, int cache_bits, uint32_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); |
| float* const cost = |
| (float*)WebPSafeMalloc((uint64_t)pix_count, sizeof(*cost)); |
| CostModel* cost_model = (CostModel*)malloc(sizeof(*cost_model)); |
| HashChain* hash_chain = (HashChain*)malloc(sizeof(*hash_chain)); |
| VP8LColorCache hashers; |
| const double mul0 = (recursive_cost_model != 0) ? 1.0 : 0.68; |
| const double mul1 = (recursive_cost_model != 0) ? 1.0 : 0.82; |
| const int min_distance_code = 2; // TODO(vikasa): tune as function of quality |
| int window_size = WINDOW_SIZE; |
| int iter_pos = 1; |
| int iter_limit = -1; |
| |
| if (cost == NULL || cost_model == NULL || hash_chain == NULL) goto Error; |
| |
| if (!HashChainInit(hash_chain, pix_count)) goto Error; |
| |
| if (use_color_cache) { |
| cc_init = VP8LColorCacheInit(&hashers, cache_bits); |
| if (!cc_init) goto Error; |
| } |
| |
| if (!CostModelBuild(cost_model, xsize, ysize, recursive_cost_model, argb, |
| quality, cache_bits)) { |
| goto Error; |
| } |
| |
| for (i = 0; i < pix_count; ++i) cost[i] = 1e38f; |
| |
| // We loop one pixel at a time, but store all currently best points to |
| // non-processed locations from this point. |
| dist_array[0] = 0; |
| GetParamsForHashChainFindCopy(quality, xsize, cache_bits, |
| &window_size, &iter_pos, &iter_limit); |
| for (i = 0; i < pix_count; ++i) { |
| double prev_cost = 0.0; |
| int shortmax; |
| if (i > 0) { |
| prev_cost = cost[i - 1]; |
| } |
| for (shortmax = 0; shortmax < 2; ++shortmax) { |
| int offset = 0; |
| int len = 0; |
| if (i < pix_count - 1) { // FindCopy reads pixels at [i] and [i + 1]. |
| int maxlen = shortmax ? 2 : MAX_LENGTH; |
| if (maxlen > pix_count - i) { |
| maxlen = pix_count - i; |
| } |
| HashChainFindCopy(hash_chain, i, xsize, argb, maxlen, |
| window_size, iter_pos, iter_limit, |
| &offset, &len); |
| } |
| if (len >= MIN_LENGTH) { |
| const int code = DistanceToPlaneCode(xsize, offset); |
| const double distance_cost = |
| prev_cost + GetDistanceCost(cost_model, code); |
| int k; |
| for (k = 1; k < len; ++k) { |
| const double cost_val = distance_cost + GetLengthCost(cost_model, k); |
| if (cost[i + k] > cost_val) { |
| cost[i + k] = (float)cost_val; |
| dist_array[i + k] = k + 1; |
| } |
| } |
| // This if is for speedup only. It roughly doubles the speed, and |
| // makes compression worse by .1 %. |
| if (len >= 128 && code <= 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) { |
| for (k = 0; k < len; ++k) { |
| VP8LColorCacheInsert(&hashers, argb[i + k]); |
| } |
| } |
| // 2) Add to the hash_chain (but cannot add the last pixel) |
| { |
| const int last = (len + i < pix_count - 1) ? len + i |
| : pix_count - 1; |
| for (k = i; k < last; ++k) { |
| HashChainInsert(hash_chain, &argb[k], k); |
| } |
| } |
| // 3) jump. |
| i += len - 1; // for loop does ++i, thus -1 here. |
| goto next_symbol; |
| } |
| } |
| } |
| if (i < pix_count - 1) { |
| HashChainInsert(hash_chain, &argb[i], i); |
| } |
| { |
| // inserting a literal pixel |
| double cost_val = prev_cost; |
| if (use_color_cache && VP8LColorCacheContains(&hashers, argb[i])) { |
| const int ix = VP8LColorCacheGetIndex(&hashers, argb[i]); |
| cost_val += GetCacheCost(cost_model, ix) * mul0; |
| } else { |
| cost_val += GetLiteralCost(cost_model, argb[i]) * mul1; |
| } |
| if (cost[i] > cost_val) { |
| cost[i] = (float)cost_val; |
| dist_array[i] = 1; // only one is inserted. |
| } |
| if (use_color_cache) VP8LColorCacheInsert(&hashers, argb[i]); |
| } |
| next_symbol: ; |
| } |
| // Last pixel still to do, it can only be a single step if not reached |
| // through cheaper means already. |
| ok = 1; |
| Error: |
| if (cc_init) VP8LColorCacheClear(&hashers); |
| HashChainDelete(hash_chain); |
| free(cost_model); |
| free(cost); |
| 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(uint32_t* const dist_array, |
| int dist_array_size, |
| uint32_t** const chosen_path, |
| int* const chosen_path_size) { |
| uint32_t* path = dist_array + dist_array_size; |
| uint32_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( |
| int xsize, int ysize, const uint32_t* const argb, |
| int quality, int cache_bits, |
| const uint32_t* const chosen_path, int chosen_path_size, |
| VP8LBackwardRefs* const refs) { |
| const int pix_count = xsize * ysize; |
| const int use_color_cache = (cache_bits > 0); |
| int size = 0; |
| int i = 0; |
| int k; |
| int ix; |
| int ok = 0; |
| int cc_init = 0; |
| int window_size = WINDOW_SIZE; |
| int iter_pos = 1; |
| int iter_limit = -1; |
| HashChain* hash_chain = (HashChain*)malloc(sizeof(*hash_chain)); |
| VP8LColorCache hashers; |
| |
| if (hash_chain == NULL || !HashChainInit(hash_chain, pix_count)) { |
| goto Error; |
| } |
| if (use_color_cache) { |
| cc_init = VP8LColorCacheInit(&hashers, cache_bits); |
| if (!cc_init) goto Error; |
| } |
| |
| refs->size = 0; |
| GetParamsForHashChainFindCopy(quality, xsize, cache_bits, |
| &window_size, &iter_pos, &iter_limit); |
| for (ix = 0; ix < chosen_path_size; ++ix, ++size) { |
| int offset = 0; |
| int len = 0; |
| int maxlen = chosen_path[ix]; |
| if (maxlen != 1) { |
| HashChainFindCopy(hash_chain, i, xsize, argb, maxlen, |
| window_size, iter_pos, iter_limit, |
| &offset, &len); |
| assert(len == maxlen); |
| refs->refs[size] = PixOrCopyCreateCopy(offset, len); |
| if (use_color_cache) { |
| for (k = 0; k < len; ++k) { |
| VP8LColorCacheInsert(&hashers, argb[i + k]); |
| } |
| } |
| { |
| const int last = (len < pix_count - 1 - i) ? len : pix_count - 1 - i; |
| for (k = 0; k < last; ++k) { |
| HashChainInsert(hash_chain, &argb[i + k], i + k); |
| } |
| } |
| i += len; |
| } else { |
| if (use_color_cache && VP8LColorCacheContains(&hashers, argb[i])) { |
| // push pixel as a color cache index |
| const int idx = VP8LColorCacheGetIndex(&hashers, argb[i]); |
| refs->refs[size] = PixOrCopyCreateCacheIdx(idx); |
| } else { |
| refs->refs[size] = PixOrCopyCreateLiteral(argb[i]); |
| } |
| if (use_color_cache) VP8LColorCacheInsert(&hashers, argb[i]); |
| if (i + 1 < pix_count) { |
| HashChainInsert(hash_chain, &argb[i], i); |
| } |
| ++i; |
| } |
| } |
| assert(size <= refs->max_size); |
| refs->size = size; |
| ok = 1; |
| Error: |
| if (cc_init) VP8LColorCacheClear(&hashers); |
| HashChainDelete(hash_chain); |
| return ok; |
| } |
| |
| // Returns 1 on success. |
| static int BackwardReferencesTraceBackwards(int xsize, int ysize, |
| int recursive_cost_model, |
| const uint32_t* const argb, |
| int quality, int cache_bits, |
| VP8LBackwardRefs* const refs) { |
| int ok = 0; |
| const int dist_array_size = xsize * ysize; |
| uint32_t* chosen_path = NULL; |
| int chosen_path_size = 0; |
| uint32_t* dist_array = |
| (uint32_t*)WebPSafeMalloc((uint64_t)dist_array_size, sizeof(*dist_array)); |
| |
| if (dist_array == NULL) goto Error; |
| |
| if (!BackwardReferencesHashChainDistanceOnly( |
| xsize, ysize, recursive_cost_model, argb, quality, cache_bits, |
| dist_array)) { |
| goto Error; |
| } |
| TraceBackwards(dist_array, dist_array_size, &chosen_path, &chosen_path_size); |
| if (!BackwardReferencesHashChainFollowChosenPath( |
| xsize, ysize, argb, quality, cache_bits, chosen_path, chosen_path_size, |
| refs)) { |
| goto Error; |
| } |
| ok = 1; |
| Error: |
| free(dist_array); |
| return ok; |
| } |
| |
| static void BackwardReferences2DLocality(int xsize, |
| VP8LBackwardRefs* const refs) { |
| int i; |
| for (i = 0; i < refs->size; ++i) { |
| if (PixOrCopyIsCopy(&refs->refs[i])) { |
| const int dist = refs->refs[i].argb_or_distance; |
| const int transformed_dist = DistanceToPlaneCode(xsize, dist); |
| refs->refs[i].argb_or_distance = transformed_dist; |
| } |
| } |
| } |
| |
| int VP8LGetBackwardReferences(int width, int height, |
| const uint32_t* const argb, |
| int quality, int cache_bits, int use_2d_locality, |
| VP8LBackwardRefs* const best) { |
| int ok = 0; |
| int lz77_is_useful; |
| VP8LBackwardRefs refs_rle, refs_lz77; |
| const int num_pix = width * height; |
| |
| VP8LBackwardRefsAlloc(&refs_rle, num_pix); |
| VP8LBackwardRefsAlloc(&refs_lz77, num_pix); |
| VP8LInitBackwardRefs(best); |
| if (refs_rle.refs == NULL || refs_lz77.refs == NULL) { |
| Error1: |
| VP8LClearBackwardRefs(&refs_rle); |
| VP8LClearBackwardRefs(&refs_lz77); |
| goto End; |
| } |
| |
| if (!BackwardReferencesHashChain(width, height, argb, cache_bits, quality, |
| &refs_lz77)) { |
| goto End; |
| } |
| // Backward Reference using RLE only. |
| BackwardReferencesRle(width, height, argb, &refs_rle); |
| |
| { |
| double bit_cost_lz77, bit_cost_rle; |
| VP8LHistogram* const histo = (VP8LHistogram*)malloc(sizeof(*histo)); |
| if (histo == NULL) goto Error1; |
| // 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); |
| free(histo); |
| } |
| |
| // Choose appropriate backward reference. |
| if (lz77_is_useful) { |
| // TraceBackwards is costly. Don't execute it at lower quality (q <= 10). |
| const int try_lz77_trace_backwards = (quality > 10); |
| *best = refs_lz77; // default guess: lz77 is better |
| VP8LClearBackwardRefs(&refs_rle); |
| if (try_lz77_trace_backwards) { |
| // Set recursion level for large images using a color cache. |
| const int recursion_level = |
| (num_pix < 320 * 200) && (cache_bits > 0) ? 1 : 0; |
| VP8LBackwardRefs refs_trace; |
| if (!VP8LBackwardRefsAlloc(&refs_trace, num_pix)) { |
| goto End; |
| } |
| if (BackwardReferencesTraceBackwards(width, height, recursion_level, argb, |
| quality, cache_bits, &refs_trace)) { |
| VP8LClearBackwardRefs(&refs_lz77); |
| *best = refs_trace; |
| } |
| } |
| } else { |
| VP8LClearBackwardRefs(&refs_lz77); |
| *best = refs_rle; |
| } |
| |
| if (use_2d_locality) BackwardReferences2DLocality(width, best); |
| |
| ok = 1; |
| |
| End: |
| if (!ok) { |
| VP8LClearBackwardRefs(best); |
| } |
| return ok; |
| } |
| |
| // Returns 1 on success. |
| static int ComputeCacheHistogram(const uint32_t* const argb, |
| int xsize, int ysize, |
| const VP8LBackwardRefs* const refs, |
| int cache_bits, |
| VP8LHistogram* const histo) { |
| int pixel_index = 0; |
| int i; |
| uint32_t k; |
| VP8LColorCache hashers; |
| const int use_color_cache = (cache_bits > 0); |
| int cc_init = 0; |
| |
| if (use_color_cache) { |
| cc_init = VP8LColorCacheInit(&hashers, cache_bits); |
| if (!cc_init) return 0; |
| } |
| |
| for (i = 0; i < refs->size; ++i) { |
| const PixOrCopy* const v = &refs->refs[i]; |
| if (PixOrCopyIsLiteral(v)) { |
| if (use_color_cache && |
| VP8LColorCacheContains(&hashers, argb[pixel_index])) { |
| // push pixel as a cache index |
| const int ix = VP8LColorCacheGetIndex(&hashers, argb[pixel_index]); |
| const PixOrCopy token = PixOrCopyCreateCacheIdx(ix); |
| VP8LHistogramAddSinglePixOrCopy(histo, &token); |
| } else { |
| VP8LHistogramAddSinglePixOrCopy(histo, v); |
| } |
| } else { |
| VP8LHistogramAddSinglePixOrCopy(histo, v); |
| } |
| if (use_color_cache) { |
| for (k = 0; k < PixOrCopyLength(v); ++k) { |
| VP8LColorCacheInsert(&hashers, argb[pixel_index + k]); |
| } |
| } |
| pixel_index += PixOrCopyLength(v); |
| } |
| assert(pixel_index == xsize * ysize); |
| (void)xsize; // xsize is not used in non-debug compilations otherwise. |
| (void)ysize; // ysize is not used in non-debug compilations otherwise. |
| if (cc_init) VP8LColorCacheClear(&hashers); |
| return 1; |
| } |
| |
| // Returns how many bits are to be used for a color cache. |
| int VP8LCalculateEstimateForCacheSize(const uint32_t* const argb, |
| int xsize, int ysize, |
| int* const best_cache_bits) { |
| int ok = 0; |
| int cache_bits; |
| double lowest_entropy = 1e99; |
| VP8LBackwardRefs refs; |
| static const double kSmallPenaltyForLargeCache = 4.0; |
| static const int quality = 30; |
| if (!VP8LBackwardRefsAlloc(&refs, xsize * ysize) || |
| !BackwardReferencesHashChain(xsize, ysize, argb, 0, quality, &refs)) { |
| goto Error; |
| } |
| for (cache_bits = 0; cache_bits <= MAX_COLOR_CACHE_BITS; ++cache_bits) { |
| double cur_entropy; |
| VP8LHistogram histo; |
| VP8LHistogramInit(&histo, cache_bits); |
| ComputeCacheHistogram(argb, xsize, ysize, &refs, cache_bits, &histo); |
| cur_entropy = VP8LHistogramEstimateBits(&histo) + |
| kSmallPenaltyForLargeCache * cache_bits; |
| if (cache_bits == 0 || cur_entropy < lowest_entropy) { |
| *best_cache_bits = cache_bits; |
| lowest_entropy = cur_entropy; |
| } |
| } |
| ok = 1; |
| Error: |
| VP8LClearBackwardRefs(&refs); |
| return ok; |
| } |
