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diff --git a/media/libwebp/enc/backward_references_enc.c b/media/libwebp/enc/backward_references_enc.c
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+// 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 <float.h>
+#include <math.h>
+
+#include "../dsp/dsp.h"
+#include "../dsp/lossless.h"
+#include "../dsp/lossless_common.h"
+#include "../enc/backward_references_enc.h"
+#include "../enc/histogram_enc.h"
+#include "../utils/color_cache_utils.h"
+#include "../utils/utils.h"
+
+#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 ((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
+
+// -----------------------------------------------------------------------------
+
+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
+};
+
+extern int VP8LDistanceToPlaneCode(int xsize, int dist);
+int VP8LDistanceToPlaneCode(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
+};
+
+extern void VP8LClearBackwardRefs(VP8LBackwardRefs* const refs);
+void VP8LClearBackwardRefs(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);
+ VP8LClearBackwardRefs(refs);
+ while (refs->free_blocks_ != NULL) {
+ PixOrCopyBlock* const next = refs->free_blocks_->next_;
+ WebPSafeFree(refs->free_blocks_);
+ refs->free_blocks_ = next;
+ }
+}
+
+// Swaps the content of two VP8LBackwardRefs.
+static void BackwardRefsSwap(VP8LBackwardRefs* const refs1,
+ VP8LBackwardRefs* const refs2) {
+ const int point_to_refs1 =
+ (refs1->tail_ != NULL && refs1->tail_ == &refs1->refs_);
+ const int point_to_refs2 =
+ (refs2->tail_ != NULL && refs2->tail_ == &refs2->refs_);
+ const VP8LBackwardRefs tmp = *refs1;
+ *refs1 = *refs2;
+ *refs2 = tmp;
+ if (point_to_refs2) refs1->tail_ = &refs1->refs_;
+ if (point_to_refs1) refs2->tail_ = &refs2->refs_;
+}
+
+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;
+}
+
+// Return 1 on success, 0 on error.
+static int BackwardRefsClone(const VP8LBackwardRefs* const from,
+ VP8LBackwardRefs* const to) {
+ const PixOrCopyBlock* block_from = from->refs_;
+ VP8LClearBackwardRefs(to);
+ while (block_from != NULL) {
+ PixOrCopyBlock* const block_to = BackwardRefsNewBlock(to);
+ if (block_to == NULL) return 0;
+ memcpy(block_to->start_, block_from->start_,
+ block_from->size_ * sizeof(PixOrCopy));
+ block_to->size_ = block_from->size_;
+ block_from = block_from->next_;
+ }
+ return 1;
+}
+
+extern void VP8LBackwardRefsCursorAdd(VP8LBackwardRefs* const refs,
+ const PixOrCopy v);
+void VP8LBackwardRefsCursorAdd(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;
+}
+
+// -----------------------------------------------------------------------------
+// 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;
+}
+
+// -----------------------------------------------------------------------------
+
+static const uint32_t kHashMultiplierHi = 0xc6a4a793u;
+static const uint32_t kHashMultiplierLo = 0x5bd1e996u;
+
+static WEBP_UBSAN_IGNORE_UNSIGNED_OVERFLOW WEBP_INLINE
+uint32_t GetPixPairHash64(const uint32_t* const argb) {
+ uint32_t key;
+ key = argb[1] * kHashMultiplierHi;
+ key += argb[0] * kHashMultiplierLo;
+ 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 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);
+ }
+ VP8LBackwardRefsCursorAdd(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;
+ }
+ VP8LClearBackwardRefs(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) {
+ VP8LBackwardRefsCursorAdd(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) {
+ VP8LBackwardRefsCursorAdd(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;
+ }
+ VP8LClearBackwardRefs(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;
+ VP8LHashChainFindCopy(hash_chain, i, &offset, &len);
+ if (len >= MIN_LENGTH) {
+ const int len_ini = len;
+ int max_reach = 0;
+ const int j_max =
+ (i + len_ini >= pix_count) ? pix_count - 1 : i + len_ini;
+ // 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 <= j_max; ++j) {
+ const int len_j = VP8LHashChainFindLength(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;
+ if (max_reach >= pix_count) break;
+ }
+ }
+ } else {
+ len = 1;
+ }
+ // Go with literal or backward reference.
+ assert(len > 0);
+ if (len == 1) {
+ AddSingleLiteral(argb[i], use_color_cache, &hashers, refs);
+ } else {
+ VP8LBackwardRefsCursorAdd(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;
+}
+
+// Compute an LZ77 by forcing matches to happen within a given distance cost.
+// We therefore limit the algorithm to the lowest 32 values in the PlaneCode
+// definition.
+#define WINDOW_OFFSETS_SIZE_MAX 32
+static int BackwardReferencesLz77Box(int xsize, int ysize,
+ const uint32_t* const argb, int cache_bits,
+ const VP8LHashChain* const hash_chain_best,
+ VP8LHashChain* hash_chain,
+ VP8LBackwardRefs* const refs) {
+ int i;
+ const int pix_count = xsize * ysize;
+ uint16_t* counts;
+ int window_offsets[WINDOW_OFFSETS_SIZE_MAX] = {0};
+ int window_offsets_new[WINDOW_OFFSETS_SIZE_MAX] = {0};
+ int window_offsets_size = 0;
+ int window_offsets_new_size = 0;
+ uint16_t* const counts_ini =
+ (uint16_t*)WebPSafeMalloc(xsize * ysize, sizeof(*counts_ini));
+ int best_offset_prev = -1, best_length_prev = -1;
+ if (counts_ini == NULL) return 0;
+
+ // counts[i] counts how many times a pixel is repeated starting at position i.
+ i = pix_count - 2;
+ counts = counts_ini + i;
+ counts[1] = 1;
+ for (; i >= 0; --i, --counts) {
+ if (argb[i] == argb[i + 1]) {
+ // Max out the counts to MAX_LENGTH.
+ counts[0] = counts[1] + (counts[1] != MAX_LENGTH);
+ } else {
+ counts[0] = 1;
+ }
+ }
+
+ // Figure out the window offsets around a pixel. They are stored in a
+ // spiraling order around the pixel as defined by VP8LDistanceToPlaneCode.
+ {
+ int x, y;
+ for (y = 0; y <= 6; ++y) {
+ for (x = -6; x <= 6; ++x) {
+ const int offset = y * xsize + x;
+ int plane_code;
+ // Ignore offsets that bring us after the pixel.
+ if (offset <= 0) continue;
+ plane_code = VP8LDistanceToPlaneCode(xsize, offset) - 1;
+ if (plane_code >= WINDOW_OFFSETS_SIZE_MAX) continue;
+ window_offsets[plane_code] = offset;
+ }
+ }
+ // For narrow images, not all plane codes are reached, so remove those.
+ for (i = 0; i < WINDOW_OFFSETS_SIZE_MAX; ++i) {
+ if (window_offsets[i] == 0) continue;
+ window_offsets[window_offsets_size++] = window_offsets[i];
+ }
+ // Given a pixel P, find the offsets that reach pixels unreachable from P-1
+ // with any of the offsets in window_offsets[].
+ for (i = 0; i < window_offsets_size; ++i) {
+ int j;
+ int is_reachable = 0;
+ for (j = 0; j < window_offsets_size && !is_reachable; ++j) {
+ is_reachable |= (window_offsets[i] == window_offsets[j] + 1);
+ }
+ if (!is_reachable) {
+ window_offsets_new[window_offsets_new_size] = window_offsets[i];
+ ++window_offsets_new_size;
+ }
+ }
+ }
+
+ hash_chain->offset_length_[0] = 0;
+ for (i = 1; i < pix_count; ++i) {
+ int ind;
+ int best_length = VP8LHashChainFindLength(hash_chain_best, i);
+ int best_offset;
+ int do_compute = 1;
+
+ if (best_length >= MAX_LENGTH) {
+ // Do not recompute the best match if we already have a maximal one in the
+ // window.
+ best_offset = VP8LHashChainFindOffset(hash_chain_best, i);
+ for (ind = 0; ind < window_offsets_size; ++ind) {
+ if (best_offset == window_offsets[ind]) {
+ do_compute = 0;
+ break;
+ }
+ }
+ }
+ if (do_compute) {
+ // Figure out if we should use the offset/length from the previous pixel
+ // as an initial guess and therefore only inspect the offsets in
+ // window_offsets_new[].
+ const int use_prev =
+ (best_length_prev > 1) && (best_length_prev < MAX_LENGTH);
+ const int num_ind =
+ use_prev ? window_offsets_new_size : window_offsets_size;
+ best_length = use_prev ? best_length_prev - 1 : 0;
+ best_offset = use_prev ? best_offset_prev : 0;
+ // Find the longest match in a window around the pixel.
+ for (ind = 0; ind < num_ind; ++ind) {
+ int curr_length = 0;
+ int j = i;
+ int j_offset =
+ use_prev ? i - window_offsets_new[ind] : i - window_offsets[ind];
+ if (j_offset < 0 || argb[j_offset] != argb[i]) continue;
+ // The longest match is the sum of how many times each pixel is
+ // repeated.
+ do {
+ const int counts_j_offset = counts_ini[j_offset];
+ const int counts_j = counts_ini[j];
+ if (counts_j_offset != counts_j) {
+ curr_length +=
+ (counts_j_offset < counts_j) ? counts_j_offset : counts_j;
+ break;
+ }
+ // The same color is repeated counts_pos times at j_offset and j.
+ curr_length += counts_j_offset;
+ j_offset += counts_j_offset;
+ j += counts_j_offset;
+ } while (curr_length <= MAX_LENGTH && j < pix_count &&
+ argb[j_offset] == argb[j]);
+ if (best_length < curr_length) {
+ best_offset =
+ use_prev ? window_offsets_new[ind] : window_offsets[ind];
+ if (curr_length >= MAX_LENGTH) {
+ best_length = MAX_LENGTH;
+ break;
+ } else {
+ best_length = curr_length;
+ }
+ }
+ }
+ }
+
+ assert(i + best_length <= pix_count);
+ assert(best_length <= MAX_LENGTH);
+ if (best_length <= MIN_LENGTH) {
+ hash_chain->offset_length_[i] = 0;
+ best_offset_prev = 0;
+ best_length_prev = 0;
+ } else {
+ hash_chain->offset_length_[i] =
+ (best_offset << MAX_LENGTH_BITS) | (uint32_t)best_length;
+ best_offset_prev = best_offset;
+ best_length_prev = best_length;
+ }
+ }
+ hash_chain->offset_length_[0] = 0;
+ WebPSafeFree(counts_ini);
+
+ return BackwardReferencesLz77(xsize, ysize, argb, cache_bits, hash_chain,
+ refs);
+}
+
+// -----------------------------------------------------------------------------
+
+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 = VP8LDistanceToPlaneCode(xsize, dist);
+ c.cur_pos->argb_or_distance = transformed_dist;
+ }
+ VP8LRefsCursorNext(&c);
+ }
+}
+
+// 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* argb, int quality,
+ const VP8LBackwardRefs* const refs,
+ int* const best_cache_bits) {
+ int i;
+ const int cache_bits_max = (quality <= 25) ? 0 : *best_cache_bits;
+ double entropy_min = MAX_ENTROPY;
+ 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;
+
+ assert(cache_bits_max >= 0 && cache_bits_max <= MAX_COLOR_CACHE_BITS);
+
+ if (cache_bits_max == 0) {
+ *best_cache_bits = 0;
+ // Local color cache is disabled.
+ return 1;
+ }
+
+ // Allocate data.
+ for (i = 0; i <= cache_bits_max; ++i) {
+ histos[i] = VP8LAllocateHistogram(i);
+ if (histos[i] == NULL) goto Error;
+ VP8LHistogramInit(histos[i], i, /*init_arrays=*/ 1);
+ if (i == 0) continue;
+ cc_init[i] = VP8LColorCacheInit(&hashers[i], i);
+ if (!cc_init[i]) goto Error;
+ }
+
+ // 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.
+ while (VP8LRefsCursorOk(&c)) {
+ const PixOrCopy* const v = c.cur_pos;
+ if (PixOrCopyIsLiteral(v)) {
+ const uint32_t pix = *argb++;
+ const uint32_t a = (pix >> 24) & 0xff;
+ const uint32_t r = (pix >> 16) & 0xff;
+ const uint32_t g = (pix >> 8) & 0xff;
+ const uint32_t b = (pix >> 0) & 0xff;
+ // The keys of the caches can be derived from the longest one.
+ int key = VP8LHashPix(pix, 32 - cache_bits_max);
+ // Do not use the color cache for cache_bits = 0.
+ ++histos[0]->blue_[b];
+ ++histos[0]->literal_[g];
+ ++histos[0]->red_[r];
+ ++histos[0]->alpha_[a];
+ // Deal with cache_bits > 0.
+ 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_[b];
+ ++histos[i]->literal_[g];
+ ++histos[i]->red_[r];
+ ++histos[i]->alpha_[a];
+ }
+ }
+ } else {
+ int code, extra_bits, extra_bits_value;
+ // We should compute the contribution of the (distance,length)
+ // histograms but those are the same independently from the cache size.
+ // As those constant contributions are in the end added to the other
+ // histogram contributions, we can ignore them, except for the length
+ // prefix that is part of the literal_ histogram.
+ int len = PixOrCopyLength(v);
+ uint32_t argb_prev = *argb ^ 0xffffffffu;
+ VP8LPrefixEncode(len, &code, &extra_bits, &extra_bits_value);
+ for (i = 0; i <= cache_bits_max; ++i) {
+ ++histos[i]->literal_[NUM_LITERAL_CODES + code];
+ }
+ // Update the color caches.
+ do {
+ if (*argb != argb_prev) {
+ // Efficiency: insert only if the color changes.
+ int key = VP8LHashPix(*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) {
+ const double entropy = VP8LHistogramEstimateBits(histos[i]);
+ if (i == 0 || entropy < entropy_min) {
+ entropy_min = entropy;
+ *best_cache_bits = i;
+ }
+ }
+ ok = 1;
+Error:
+ for (i = 0; i <= cache_bits_max; ++i) {
+ if (cc_init[i]) VP8LColorCacheClear(&hashers[i]);
+ VP8LFreeHistogram(histos[i]);
+ }
+ return ok;
+}
+
+// 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* const refs_lz77) {
+ *cache_bits = 0;
+ if (!BackwardReferencesLz77(width, height, argb, 0, hash_chain, refs_lz77)) {
+ return NULL;
+ }
+ BackwardReferences2DLocality(width, refs_lz77);
+ return refs_lz77;
+}
+
+extern int VP8LBackwardReferencesTraceBackwards(
+ int xsize, int ysize, const uint32_t* const argb, int cache_bits,
+ const VP8LHashChain* const hash_chain,
+ const VP8LBackwardRefs* const refs_src, VP8LBackwardRefs* const refs_dst);
+static int GetBackwardReferences(int width, int height,
+ const uint32_t* const argb, int quality,
+ int lz77_types_to_try, int cache_bits_max,
+ int do_no_cache,
+ const VP8LHashChain* const hash_chain,
+ VP8LBackwardRefs* const refs,
+ int* const cache_bits_best) {
+ VP8LHistogram* histo = NULL;
+ int i, lz77_type;
+ // Index 0 is for a color cache, index 1 for no cache (if needed).
+ int lz77_types_best[2] = {0, 0};
+ double bit_costs_best[2] = {DBL_MAX, DBL_MAX};
+ VP8LHashChain hash_chain_box;
+ VP8LBackwardRefs* const refs_tmp = &refs[do_no_cache ? 2 : 1];
+ int status = 0;
+ memset(&hash_chain_box, 0, sizeof(hash_chain_box));
+
+ histo = VP8LAllocateHistogram(MAX_COLOR_CACHE_BITS);
+ if (histo == NULL) goto Error;
+
+ for (lz77_type = 1; lz77_types_to_try;
+ lz77_types_to_try &= ~lz77_type, lz77_type <<= 1) {
+ int res = 0;
+ double bit_cost = 0.;
+ if ((lz77_types_to_try & lz77_type) == 0) continue;
+ switch (lz77_type) {
+ case kLZ77RLE:
+ res = BackwardReferencesRle(width, height, argb, 0, refs_tmp);
+ break;
+ case kLZ77Standard:
+ // Compute LZ77 with no cache (0 bits), as the ideal LZ77 with a color
+ // cache is not that different in practice.
+ res = BackwardReferencesLz77(width, height, argb, 0, hash_chain,
+ refs_tmp);
+ break;
+ case kLZ77Box:
+ if (!VP8LHashChainInit(&hash_chain_box, width * height)) goto Error;
+ res = BackwardReferencesLz77Box(width, height, argb, 0, hash_chain,
+ &hash_chain_box, refs_tmp);
+ break;
+ default:
+ assert(0);
+ }
+ if (!res) goto Error;
+
+ // Start with the no color cache case.
+ for (i = 1; i >= 0; --i) {
+ int cache_bits = (i == 1) ? 0 : cache_bits_max;
+
+ if (i == 1 && !do_no_cache) continue;
+
+ if (i == 0) {
+ // Try with a color cache.
+ if (!CalculateBestCacheSize(argb, quality, refs_tmp, &cache_bits)) {
+ goto Error;
+ }
+ if (cache_bits > 0) {
+ if (!BackwardRefsWithLocalCache(argb, cache_bits, refs_tmp)) {
+ goto Error;
+ }
+ }
+ }
+
+ if (i == 0 && do_no_cache && cache_bits == 0) {
+ // No need to re-compute bit_cost as it was computed at i == 1.
+ } else {
+ VP8LHistogramCreate(histo, refs_tmp, cache_bits);
+ bit_cost = VP8LHistogramEstimateBits(histo);
+ }
+
+ if (bit_cost < bit_costs_best[i]) {
+ if (i == 1) {
+ // Do not swap as the full cache analysis would have the wrong
+ // VP8LBackwardRefs to start with.
+ if (!BackwardRefsClone(refs_tmp, &refs[1])) goto Error;
+ } else {
+ BackwardRefsSwap(refs_tmp, &refs[0]);
+ }
+ bit_costs_best[i] = bit_cost;
+ lz77_types_best[i] = lz77_type;
+ if (i == 0) *cache_bits_best = cache_bits;
+ }
+ }
+ }
+ assert(lz77_types_best[0] > 0);
+ assert(!do_no_cache || lz77_types_best[1] > 0);
+
+ // Improve on simple LZ77 but only for high quality (TraceBackwards is
+ // costly).
+ for (i = 1; i >= 0; --i) {
+ if (i == 1 && !do_no_cache) continue;
+ if ((lz77_types_best[i] == kLZ77Standard ||
+ lz77_types_best[i] == kLZ77Box) &&
+ quality >= 25) {
+ const VP8LHashChain* const hash_chain_tmp =
+ (lz77_types_best[i] == kLZ77Standard) ? hash_chain : &hash_chain_box;
+ const int cache_bits = (i == 1) ? 0 : *cache_bits_best;
+ if (VP8LBackwardReferencesTraceBackwards(width, height, argb, cache_bits,
+ hash_chain_tmp, &refs[i],
+ refs_tmp)) {
+ double bit_cost_trace;
+ VP8LHistogramCreate(histo, refs_tmp, cache_bits);
+ bit_cost_trace = VP8LHistogramEstimateBits(histo);
+ if (bit_cost_trace < bit_costs_best[i]) {
+ BackwardRefsSwap(refs_tmp, &refs[i]);
+ }
+ }
+ }
+
+ BackwardReferences2DLocality(width, &refs[i]);
+
+ if (i == 1 && lz77_types_best[0] == lz77_types_best[1] &&
+ *cache_bits_best == 0) {
+ // If the best cache size is 0 and we have the same best LZ77, just copy
+ // the data over and stop here.
+ if (!BackwardRefsClone(&refs[1], &refs[0])) goto Error;
+ break;
+ }
+ }
+ status = 1;
+
+Error:
+ VP8LHashChainClear(&hash_chain_box);
+ VP8LFreeHistogram(histo);
+ return status;
+}
+
+WebPEncodingError VP8LGetBackwardReferences(
+ int width, int height, const uint32_t* const argb, int quality,
+ int low_effort, int lz77_types_to_try, int cache_bits_max, int do_no_cache,
+ const VP8LHashChain* const hash_chain, VP8LBackwardRefs* const refs,
+ int* const cache_bits_best) {
+ if (low_effort) {
+ VP8LBackwardRefs* refs_best;
+ *cache_bits_best = cache_bits_max;
+ refs_best = GetBackwardReferencesLowEffort(
+ width, height, argb, cache_bits_best, hash_chain, refs);
+ if (refs_best == NULL) return VP8_ENC_ERROR_OUT_OF_MEMORY;
+ // Set it in first position.
+ BackwardRefsSwap(refs_best, &refs[0]);
+ } else {
+ if (!GetBackwardReferences(width, height, argb, quality, lz77_types_to_try,
+ cache_bits_max, do_no_cache, hash_chain, refs,
+ cache_bits_best)) {
+ return VP8_ENC_ERROR_OUT_OF_MEMORY;
+ }
+ }
+ return VP8_ENC_OK;
+}
generated by cgit v1.2.3 (git 2.26.2) at 2024-11-09 16:38:42 +0000