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Optimize BackwardReferences for RLE encoding.

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Updated BackwardReferencesRle method by utilizing the local color cache.
Also changed the name of method BackwardReferencesHashChain to
BackwardReferencesLz77 to reflect the LZ77 coding.

For the 1000 image corpus, this change saves 0.2% bytes
(at default settings) and is 2-5% faster to encode.

Change-Id: Ic3f288253b3bbb101a69945a80994c3fd0917f8b
This commit is contained in:
Vikas Arora 2014-11-04 08:10:31 -08:00
parent 5798eee6be
commit c8581b06e1
1 changed files with 47 additions and 38 deletions
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85
src/enc/backward_references.c
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@ -313,38 +313,6 @@ static int HashChainFindCopy(const VP8LHashChain* const p,
return (best_length >= MIN_LENGTH);
}
static WEBP_INLINE void PushBackCopy(VP8LBackwardRefs* const refs, int length) {
while (length >= MAX_LENGTH) {
BackwardRefsCursorAdd(refs, PixOrCopyCreateCopy(1, MAX_LENGTH));
length -= MAX_LENGTH;
}
if (length > 0) {
BackwardRefsCursorAdd(refs, PixOrCopyCreateCopy(1, length));
}
}
static int BackwardReferencesRle(int xsize, int ysize,
const uint32_t* const argb,
VP8LBackwardRefs* const refs) {
const int pix_count = xsize * ysize;
int match_len = 0;
int i;
ClearBackwardRefs(refs);
PushBackCopy(refs, match_len); // i=0 case
BackwardRefsCursorAdd(refs, PixOrCopyCreateLiteral(argb[0]));
for (i = 1; i < pix_count; ++i) {
if (argb[i] == argb[i - 1]) {
++match_len;
} else {
PushBackCopy(refs, match_len);
match_len = 0;
BackwardRefsCursorAdd(refs, PixOrCopyCreateLiteral(argb[i]));
}
}
PushBackCopy(refs, match_len);
return !refs->error_;
}
static void AddSingleLiteral(uint32_t pixel, int use_color_cache,
VP8LColorCache* const hashers,
VP8LBackwardRefs* const refs) {
@ -360,7 +328,48 @@ static void AddSingleLiteral(uint32_t pixel, int use_color_cache,
BackwardRefsCursorAdd(refs, v);
}
static int BackwardReferencesHashChain(int xsize, int ysize,
static WEBP_INLINE void PushBackCopy(VP8LBackwardRefs* const refs, int length) {
while (length >= MAX_LENGTH) {
BackwardRefsCursorAdd(refs, PixOrCopyCreateCopy(1, MAX_LENGTH));
length -= MAX_LENGTH;
}
if (length > 0) {
BackwardRefsCursorAdd(refs, PixOrCopyCreateCopy(1, length));
}
}
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 match_len = 0;
int i;
int cc_init = 0;
const int use_color_cache = (cache_bits > 0);
VP8LColorCache hashers;
if (use_color_cache) {
cc_init = VP8LColorCacheInit(&hashers, cache_bits);
if (!cc_init) return 0;
}
ClearBackwardRefs(refs);
// Add first pixel as literal.
AddSingleLiteral(argb[0], use_color_cache, &hashers, refs);
for (i = 1; i < pix_count; ++i) {
if (argb[i] == argb[i - 1]) {
++match_len;
} else {
PushBackCopy(refs, match_len);
match_len = 0;
AddSingleLiteral(argb[i], use_color_cache, &hashers, refs);
}
}
PushBackCopy(refs, match_len);
if (cc_init) VP8LColorCacheClear(&hashers);
return !refs->error_;
}
static int BackwardReferencesLz77(int xsize, int ysize,
const uint32_t* const argb,
int cache_bits, int quality,
VP8LHashChain* const hash_chain,
@ -813,11 +822,11 @@ VP8LBackwardRefs* VP8LGetBackwardReferences(
VP8LHistogram* const histo = VP8LAllocateHistogram(cache_bits);
if (histo == NULL) return NULL;
if (!BackwardReferencesHashChain(width, height, argb, cache_bits, quality,
hash_chain, refs_lz77)) {
if (!BackwardReferencesLz77(width, height, argb, cache_bits, quality,
hash_chain, refs_lz77)) {
goto Error;
}
if (!BackwardReferencesRle(width, height, argb, refs_rle)) {
if (!BackwardReferencesRle(width, height, argb, cache_bits, refs_rle)) {
goto Error;
}
@ -943,8 +952,8 @@ int VP8LCalculateEstimateForCacheSize(const uint32_t* const argb,
return 1;
}
if (!BackwardReferencesHashChain(xsize, ysize, argb, 0, quality, hash_chain,
refs)) {
if (!BackwardReferencesLz77(xsize, ysize, argb, 0, quality, hash_chain,
refs)) {
return 0;
}
// Do a binary search to find the optimal entropy for cache_bits.