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Tune Lossless compression for lower qualities.

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This is required for WebP lossy+Alpha images, where Alpha channel is taking
60-70% of the compression (CPU) cycles.

Also evaluated on 1000 PNG corpus and overall compression speed
is 15-40% better for lossy (PNG+Alpha) compression.
The pure lossless compression numbers are almost same (or little
better) with this change.

Change-Id: I9e5ae7372ed6227a9a5b64cd9cff84c747195a57
This commit is contained in:
Vikas Arora
2013-03-05 22:05:00 +00:00
committed by James Zern
parent 19eb012c55
commit 0478b5d214
3 changed files with 6 additions and 11 deletions
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8
src/enc/backward_references.c
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@ -555,10 +555,10 @@ static int BackwardReferencesHashChainDistanceOnly(
}
// 2) Add to the hash_chain (but cannot add the last pixel)
{
const int last = (len < pix_count - 1 - i) ? len
: pix_count - 1 - i;
for (k = 0; k < last; ++k) {
HashChainInsert(hash_chain, &argb[i + k], i + k);
const int last = (len + i < pix_count - 1) ? len + i
: pix_count - 1;
for (k = i; k < last; ++k) {
HashChainInsert(hash_chain, &argb[k], k);
}
}
// 3) jump.