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Unified Diff: third_party/libwebp/enc/backward_references.c

Issue 2651883004: libwebp-0.6.0-rc1 (Closed)
Patch Set: Created 3 years, 11 months ago
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Index: third_party/libwebp/enc/backward_references.c
diff --git a/third_party/libwebp/enc/backward_references.c b/third_party/libwebp/enc/backward_references.c
deleted file mode 100644
index 136a24a8c31c810bd8b1b228f07ad2c9681de364..0000000000000000000000000000000000000000
--- a/third_party/libwebp/enc/backward_references.c
+++ /dev/null
@@ -1,1715 +0,0 @@
-// 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.h"
-#include "./histogram.h"
-#include "../dsp/lossless.h"
-#include "../dsp/dsp.h"
-#include "../utils/color_cache.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)
-
-// Bounds for the match length.
-#define MIN_LENGTH 2
-// 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 (0xc6a4a793U)
-#define HASH_MULTIPLIER_LO (0x5bd1e996U)
-
-static WEBP_INLINE uint32_t GetPixPairHash64(const uint32_t* const argb) {
- uint32_t key;
- key = argb[1] * HASH_MULTIPLIER_HI;
- key += argb[0] * HASH_MULTIPLIER_LO;
- 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) {
- const int size = xsize * ysize;
- const int iter_max = GetMaxItersForQuality(quality);
- const int iter_min = iter_max - quality / 10;
- const uint32_t window_size = GetWindowSizeForHashChain(quality, xsize);
- int pos;
- 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(p->size_ != 0);
- assert(p->offset_length_ != NULL);
-
- 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.
- for (pos = 0; pos < size - 1; ++pos) {
- const uint32_t hash_code = GetPixPairHash64(argb + pos);
- chain[pos] = hash_to_first_index[hash_code];
- hash_to_first_index[hash_code] = 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).
- p->offset_length_[0] = p->offset_length_[size - 1] = 0;
- for (base_position = size - 2 < 0 ? 0 : 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;
- 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;
-
- for (pos = chain[base_position]; pos >= min_pos; pos = chain[pos]) {
- int curr_length;
- if (--iter < 0) {
- break;
- }
- assert(base_position > (uint32_t)pos);
-
- curr_length =
- FindMatchLength(argb + pos, argb_start, best_length, max_len);
- if (best_length < curr_length) {
- best_length = curr_length;
- best_distance = base_position - pos;
- // Stop if we have reached the maximum length. Otherwise, make sure
- // we have executed a minimum number of iterations depending on the
- // quality.
- if ((best_length == MAX_LENGTH) ||
- (curr_length >= length_max && iter < iter_min)) {
- 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 kMinLength = 4;
- 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 >= kMinLength) {
- 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 >= kMinLength) {
- 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 + 1) {
- 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 + 1 ? 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];
- if (use_color_cache && VP8LColorCacheContains(hashers, color)) {
- const double mul0 = 0.68;
- const int ix = VP8LColorCacheGetIndex(hashers, color);
- 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 >= MIN_LENGTH) {
- 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 > MIN_LENGTH) {
- int code_min_length;
- double cost_total;
- offset = HashChainFindOffset(hash_chain, i);
- code_min_length = DistanceToPlaneCode(xsize, offset);
- cost_total = prev_cost +
- GetDistanceCost(cost_model, code_min_length) +
- 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 { // len < MIN_LENGTH
- 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;
- if (use_color_cache && VP8LColorCacheContains(&hashers, argb[i])) {
- // push pixel as a color cache index
- const int idx = VP8LColorCacheGetIndex(&hashers, argb[i]);
- 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);
- }
-}
-
-// Returns entropy for the given cache bits.
-static double ComputeCacheEntropy(const uint32_t* argb,
- const VP8LBackwardRefs* const refs,
- int cache_bits) {
- const int use_color_cache = (cache_bits > 0);
- int cc_init = 0;
- double entropy = MAX_ENTROPY;
- const double kSmallPenaltyForLargeCache = 4.0;
- VP8LColorCache hashers;
- VP8LRefsCursor c = VP8LRefsCursorInit(refs);
- VP8LHistogram* histo = VP8LAllocateHistogram(cache_bits);
- if (histo == NULL) goto Error;
-
- if (use_color_cache) {
- cc_init = VP8LColorCacheInit(&hashers, cache_bits);
- if (!cc_init) goto Error;
- }
- if (!use_color_cache) {
- while (VP8LRefsCursorOk(&c)) {
- VP8LHistogramAddSinglePixOrCopy(histo, c.cur_pos);
- VP8LRefsCursorNext(&c);
- }
- } else {
- while (VP8LRefsCursorOk(&c)) {
- const PixOrCopy* const v = c.cur_pos;
- if (PixOrCopyIsLiteral(v)) {
- const uint32_t pix = *argb++;
- const uint32_t key = VP8LColorCacheGetIndex(&hashers, pix);
- if (VP8LColorCacheLookup(&hashers, key) == pix) {
- ++histo->literal_[NUM_LITERAL_CODES + NUM_LENGTH_CODES + key];
- } else {
- VP8LColorCacheSet(&hashers, key, pix);
- ++histo->blue_[pix & 0xff];
- ++histo->literal_[(pix >> 8) & 0xff];
- ++histo->red_[(pix >> 16) & 0xff];
- ++histo->alpha_[pix >> 24];
- }
- } else {
- int len = PixOrCopyLength(v);
- int code, extra_bits;
- VP8LPrefixEncodeBits(len, &code, &extra_bits);
- ++histo->literal_[NUM_LITERAL_CODES + code];
- VP8LPrefixEncodeBits(PixOrCopyDistance(v), &code, &extra_bits);
- ++histo->distance_[code];
- do {
- VP8LColorCacheInsert(&hashers, *argb++);
- } while(--len != 0);
- }
- VP8LRefsCursorNext(&c);
- }
- }
- entropy = VP8LHistogramEstimateBits(histo) +
- kSmallPenaltyForLargeCache * cache_bits;
- Error:
- if (cc_init) VP8LColorCacheClear(&hashers);
- VP8LFreeHistogram(histo);
- return entropy;
-}
-
-// 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 eval_low = 1;
- int eval_high = 1;
- double entropy_low = MAX_ENTROPY;
- double entropy_high = MAX_ENTROPY;
- const double cost_mul = 5e-4;
- int cache_bits_low = 0;
- int cache_bits_high = (quality <= 25) ? 0 : *best_cache_bits;
-
- 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;
- }
- if (!BackwardReferencesLz77(xsize, ysize, argb, cache_bits_low, hash_chain,
- refs)) {
- return 0;
- }
- // Do a binary search to find the optimal entropy for cache_bits.
- while (eval_low || eval_high) {
- if (eval_low) {
- entropy_low = ComputeCacheEntropy(argb, refs, cache_bits_low);
- entropy_low += entropy_low * cache_bits_low * cost_mul;
- eval_low = 0;
- }
- if (eval_high) {
- entropy_high = ComputeCacheEntropy(argb, refs, cache_bits_high);
- entropy_high += entropy_high * cache_bits_high * cost_mul;
- eval_high = 0;
- }
- if (entropy_high < entropy_low) {
- const int prev_cache_bits_low = cache_bits_low;
- *best_cache_bits = cache_bits_high;
- cache_bits_low = (cache_bits_low + cache_bits_high) / 2;
- if (cache_bits_low != prev_cache_bits_low) eval_low = 1;
- } else {
- *best_cache_bits = cache_bits_low;
- cache_bits_high = (cache_bits_low + cache_bits_high) / 2;
- if (cache_bits_high != cache_bits_low) eval_high = 1;
- }
- }
- *lz77_computed = 1;
- 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;
- if (VP8LColorCacheContains(&hashers, argb_literal)) {
- const int ix = VP8LColorCacheGetIndex(&hashers, 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);
- }
-}
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