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Provide one entry point for backward references.

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The new method VP8LGetBackwardReferences hides internal
heuristics used for choosing RLE or LZ77 based refs.
- Tuned VP8LHashChainFindCopy for better compression at higher Q.
- Refactored code.
- Removed the unused method VP8LVerifyBackwardReferences.

Change-Id: Ibb7bb072bab5a49a001577a20d88226f52e6c663
This commit is contained in:
Vikas Arora
2012-05-09 12:11:55 +05:30
parent c4ccab6463
commit e7167a2b95
3 changed files with 158 additions and 235 deletions
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38
src/enc/backward_references.h
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@ -206,38 +206,12 @@ static WEBP_INLINE int VP8LBackwardRefsAlloc(VP8LBackwardRefs* const refs,
return 1;
}
// Ridiculously simple backward references for images where it is unlikely
// that there are large backward references (photos).
void VP8LBackwardReferencesRle(
int xsize, int ysize, const uint32_t* const argb,
VP8LBackwardRefs* const refs);
// This is a simple fast function for obtaining backward references
// based on simple heuristics. Returns 1 on success.
int VP8LBackwardReferencesHashChain(
int xsize, int ysize, int use_color_cache, const uint32_t* const argb,
int cache_bits, int quality, VP8LBackwardRefs* const refs);
// This method looks for a shortest path through the backward reference
// network based on a cost model generated by a first round of compression.
// Returns 1 on success.
int VP8LBackwardReferencesTraceBackwards(
int xsize, int ysize, int recursive_cost_model, int use_color_cache,
const uint32_t* const argb, int cache_bits, VP8LBackwardRefs* const refs);
// Convert backward references that are of linear distance along
// the image scan lines to have a 2d locality indexing where
// smaller values are used for backward references that are close by.
void VP8LBackwardReferences2DLocality(int xsize, VP8LBackwardRefs* const refs);
// Internals of locality transform exposed for testing use.
int VP8LDistanceToPlaneCode(int xsize, int distance);
// Returns true if the given backward references actually produce
// the image given in tuple (argb, xsize, ysize).
int VP8LVerifyBackwardReferences(
const uint32_t* const argb, int xsize, int ysize, int cache_bits,
const VP8LBackwardRefs* const refs);
// Evaluates best possible backward references for specified quality.
// Further optimize for 2D locality if use_2d_locality flag is set.
int VP8LGetBackwardReferences(int width, int height,
const uint32_t* const argb,
int quality, int cache_bits, int use_2d_locality,
VP8LBackwardRefs* const best);
// Produce an estimate for a good color cache size for the image.
int VP8LCalculateEstimateForCacheSize(