dany/libwebp
1
0
Fork 0
mirror of https://github.com/webmproject/libwebp.git synced 2024-12-28 14:38:21 +01:00
Code Issues Actions Packages Projects Releases Wiki Activity

lossless: Remove about 25 % of the speed degradation

Browse Source 
introduced in:
"lossless: 0.37 % compression density improvement"

Uses the statistics of red and blue histograms to decide if to run
cross color correction at all.

Improves compression density by 0.02 % or so.

Change-Id: I47429557e9cdbd9fa90c584696f241b17427d73f
This commit is contained in:
Jyrki Alakuijala 2015-06-17 17:28:34 +00:00 committed by James Zern
parent 2cce031704
commit d92453f381
1 changed files with 32 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

48
src/enc/vp8l.c
View File

@ -210,7 +210,9 @@ typedef enum {
static int AnalyzeEntropy(const uint32_t* argb, static int AnalyzeEntropy(const uint32_t* argb,
int width, int height, int argb_stride, int width, int height, int argb_stride,
double entropy[kNumEntropyIx]) { int use_palette,
EntropyIx* const min_entropy_ix,
int* const red_and_blue_always_zero) {
// Allocate histogram set with cache_bits = 0. // Allocate histogram set with cache_bits = 0.
VP8LHistogramSet* const histo_set = VP8LAllocateHistogramSet(5, 0); VP8LHistogramSet* const histo_set = VP8LAllocateHistogramSet(5, 0);
if (histo_set != NULL) { if (histo_set != NULL) {
@ -242,8 +244,29 @@ static int AnalyzeEntropy(const uint32_t* argb,
prev_row = curr_row; prev_row = curr_row;
curr_row += argb_stride; curr_row += argb_stride;
} }
for (i = 0; i < kNumEntropyIx; ++i) { {
entropy[i] = VP8LHistogramEstimateBitsBulk(histo[i]); double entropy[kNumEntropyIx];
EntropyIx k;
EntropyIx last_mode_to_analyze =
use_palette ? kPalette : kSpatialSubGreen;
*min_entropy_ix = kDirect;
for (k = kDirect; k <= last_mode_to_analyze; ++k) {
entropy[k] = VP8LHistogramEstimateBitsBulk(histo[k]);
if (k == kDirect || entropy[*min_entropy_ix] >= entropy[k]) {
*min_entropy_ix = k;
}
}
*red_and_blue_always_zero = 1;
// Let's check if the histogram of the chosen entropy mode has
// non-zero red and blue values. If all are zero, we can later skip
// the cross color optimization.
for (i = 1; i < 256; ++i) {
if ((histo[*min_entropy_ix]->red_[i] |
histo[*min_entropy_ix]->blue_[i]) != 0) {
*red_and_blue_always_zero = 0;
break;
}
}
} }
VP8LFreeHistogramSet(histo_set); VP8LFreeHistogramSet(histo_set);
return 1; return 1;
@ -301,26 +324,19 @@ static int AnalyzeAndInit(VP8LEncoder* const enc) {
enc->use_subtract_green_ = !enc->use_palette_; enc->use_subtract_green_ = !enc->use_palette_;
enc->use_cross_color_ = 0; enc->use_cross_color_ = 0;
} else { } else {
double entropy[kNumEntropyIx]; int red_and_blue_always_zero;
EntropyIx min_entropy_ix = kDirect; EntropyIx min_entropy_ix;
EntropyIx i = kDirect;
EntropyIx last_mode_to_analyze;
if (!AnalyzeEntropy(pic->argb, width, height, pic->argb_stride, if (!AnalyzeEntropy(pic->argb, width, height, pic->argb_stride,
&entropy[0])) { enc->use_palette_, &min_entropy_ix,
&red_and_blue_always_zero)) {
return 0; return 0;
} }
entropy[kPalette] -= 10.; // Small bias in favor of using the palette.
last_mode_to_analyze = enc->use_palette_ ? kPalette : kSpatialSubGreen;
for (i = 1; i <= last_mode_to_analyze; ++i) {
if (entropy[min_entropy_ix] > entropy[i]) {
min_entropy_ix = i;
}
}
enc->use_palette_ = (min_entropy_ix == kPalette); enc->use_palette_ = (min_entropy_ix == kPalette);
enc->use_subtract_green_ = enc->use_subtract_green_ =
(min_entropy_ix == kSubGreen) || (min_entropy_ix == kSpatialSubGreen); (min_entropy_ix == kSubGreen) || (min_entropy_ix == kSpatialSubGreen);
enc->use_cross_color_ = enc->use_predict_ = enc->use_predict_ =
(min_entropy_ix == kSpatial) || (min_entropy_ix == kSpatialSubGreen); (min_entropy_ix == kSpatial) || (min_entropy_ix == kSpatialSubGreen);
enc->use_cross_color_ = red_and_blue_always_zero ? 0 : enc->use_predict_;
} }
if (!VP8LHashChainInit(&enc->hash_chain_, pix_cnt)) return 0; if (!VP8LHashChainInit(&enc->hash_chain_, pix_cnt)) return 0;