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WebPAnimEncoder: FlattenSimilarPixels(): look for similar

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not exactly same.

Based on lossy WebP quality setting, ignore minor differences when
flattening
similar blocks.

For 6k set, at default quality with '-min_size' option, improves
compression by 0.3%

Change-Id: Ifcb64219f941e869eb2643e231220b278aad4cd4
This commit is contained in:
Urvang Joshi 2016-04-04 20:27:52 +00:00 committed by James Zern
parent 238cdcdbe1
commit 31f2b8d8e1
1 changed files with 43 additions and 12 deletions
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43
src/mux/anim_encode.c
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@ -596,7 +596,7 @@ static uint32_t RectArea(const FrameRect* const rect) {
return (uint32_t)rect->width_ * rect->height_;
}
static int IsBlendingPossible(const WebPPicture* const src,
static int IsLosslessBlendingPossible(const WebPPicture* const src,
const WebPPicture* const dst,
const FrameRect* const rect) {
int i, j;
@ -618,6 +618,31 @@ static int IsBlendingPossible(const WebPPicture* const src,
return 1;
}
static int IsLossyBlendingPossible(const WebPPicture* const src,
const WebPPicture* const dst,
const FrameRect* const rect,
float quality) {
const int max_allowed_diff_lossy = QualityToMaxDiff(quality);
int i, j;
assert(src->width == dst->width && src->height == dst->height);
assert(rect->x_offset_ + rect->width_ <= dst->width);
assert(rect->y_offset_ + rect->height_ <= dst->height);
for (j = rect->y_offset_; j < rect->y_offset_ + rect->height_; ++j) {
for (i = rect->x_offset_; i < rect->x_offset_ + rect->width_; ++i) {
const uint32_t src_pixel = src->argb[j * src->argb_stride + i];
const uint32_t dst_pixel = dst->argb[j * dst->argb_stride + i];
const uint32_t dst_alpha = dst_pixel >> 24;
if (dst_alpha != 0xff &&
!PixelsAreSimilar(src_pixel, dst_pixel, max_allowed_diff_lossy)) {
// In this case, if we use blending, we can't attain the desired
// 'dst_pixel' value for this pixel. So, blending is not possible.
return 0;
}
}
}
return 1;
}
#define MIN_COLORS_LOSSY 31 // Don't try lossy below this threshold.
#define MAX_COLORS_LOSSLESS 194 // Don't try lossless above this threshold.
#define MAX_COLOR_COUNT 256 // Power of 2 greater than MAX_COLORS_LOSSLESS.
@ -696,9 +721,12 @@ static void IncreaseTransparency(const WebPPicture* const src,
// Replace similar blocks of pixels by a 'see-through' transparent block
// with uniform average color.
// Assumes lossy compression is being used.
static void FlattenSimilarBlocks(const WebPPicture* const src,
const FrameRect* const rect,
WebPPicture* const dst) {
WebPPicture* const dst,
float quality) {
const int max_allowed_diff_lossy = QualityToMaxDiff(quality);
int i, j;
const int block_size = 8;
const int y_start = (rect->y_offset_ + block_size) & ~(block_size - 1);
@ -721,7 +749,8 @@ static void FlattenSimilarBlocks(const WebPPicture* const src,
const uint32_t src_pixel = psrc[x + y * src->argb_stride];
const int alpha = src_pixel >> 24;
if (alpha == 0xff &&
src_pixel == pdst[x + y * dst->argb_stride]) {
PixelsAreSimilar(src_pixel, pdst[x + y * dst->argb_stride],
max_allowed_diff_lossy)) {
++cnt;
avg_r += (src_pixel >> 16) & 0xff;
avg_g += (src_pixel >> 8) & 0xff;
@ -844,10 +873,11 @@ static WebPEncodingError GenerateCandidates(
is_dispose_none ? &enc->prev_canvas_ : &enc->prev_canvas_disposed_;
const int use_blending_ll =
!is_key_frame &&
IsBlendingPossible(prev_canvas, curr_canvas, &params->rect_ll_);
IsLosslessBlendingPossible(prev_canvas, curr_canvas, &params->rect_ll_);
const int use_blending_lossy =
!is_key_frame &&
IsBlendingPossible(prev_canvas, curr_canvas, &params->rect_lossy_);
IsLossyBlendingPossible(prev_canvas, curr_canvas, &params->rect_lossy_,
config_lossy->quality);
// Pick candidates to be tried.
if (!enc->options_.allow_mixed) {
@ -873,7 +903,8 @@ static WebPEncodingError GenerateCandidates(
if (candidate_lossy->evaluate_) {
CopyCurrentCanvas(enc);
if (use_blending_lossy) {
FlattenSimilarBlocks(prev_canvas, &params->rect_lossy_, curr_canvas);
FlattenSimilarBlocks(prev_canvas, &params->rect_lossy_, curr_canvas,
config_lossy->quality);
enc->curr_canvas_copy_modified_ = 1;
}
error_code =