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Apply the RLE heuristic to LZ77.

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Change-Id: I7317eed7e017ee8981f40fcf1737f97e0e3a238c
This commit is contained in:
Vincent Rabaud
2016-07-14 19:21:07 +02:00
parent fe57273736
commit 2a5c417c68
3 changed files with 38 additions and 17 deletions
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21
src/enc/backward_references.c
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@ -242,7 +242,8 @@ static WEBP_INLINE int MaxFindCopyLength(int len) {
}
int VP8LHashChainFill(VP8LHashChain* const p, int quality,
const uint32_t* const argb, int xsize, int ysize) {
const uint32_t* const argb, int xsize, int ysize,
int low_effort) {
const int size = xsize * ysize;
const int iter_max = GetMaxItersForQuality(quality);
const int iter_min = iter_max - quality / 10;
@ -285,7 +286,23 @@ int VP8LHashChainFill(VP8LHashChain* const p, int quality,
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]) {
pos = chain[base_position];
if (!low_effort) {
// Heuristic: use the comparison with the above line as an initialization.
if (base_position >= (uint32_t)xsize) {
const int 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;
// Skip the for loop if we already have the maximum.
if (best_length == MAX_LENGTH) pos = min_pos - 1;
}
for (; pos >= min_pos; pos = chain[pos]) {
int curr_length;
if (--iter < 0) {
break;