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Add image-hint for low-color images.

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For low-color images, it may be better to not use color-palettes.
Users should treat this as one another hint (as with Photo &
Picture) and another parameter for tuning the compression density.
The optimum compression can still be obtained by running (outer loop)
compression with all possible tunable parameters.

Change-Id: Icb1a4face2a84774e16e801aee4a8ae97e232e8a
This commit is contained in:
Vikas Arora
2012-07-31 23:07:52 -07:00
parent 4eb7aa64da
commit dd1c3873fe
6 changed files with 10 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
src/enc/config.c
View File

@ -120,7 +120,7 @@ int WebPValidateConfig(const WebPConfig* config) {
return 0;
if (config->lossless < 0 || config->lossless > 1)
return 0;
if (config->image_hint > WEBP_HINT_PHOTO)
if (config->image_hint >= WEBP_HINT_LAST)
return 0;
return 1;
}

3
src/enc/vp8l.c
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@ -141,7 +141,7 @@ static int VP8LEncAnalyze(VP8LEncoder* const enc, WebPImageHint image_hint) {
const WebPPicture* const pic = enc->pic_;
assert(pic != NULL && pic->argb != NULL);
enc->use_palette_ =
enc->use_palette_ = (image_hint == WEBP_HINT_GRAPH) ? 0 :
AnalyzeAndCreatePalette(pic, enc->palette_, &enc->palette_size_);
if (!enc->use_palette_) {
if (image_hint == WEBP_HINT_DEFAULT) {
@ -162,7 +162,6 @@ static int VP8LEncAnalyze(VP8LEncoder* const enc, WebPImageHint image_hint) {
return 1;
}
static int GetHuffBitLengthsAndCodes(
const VP8LHistogramSet* const histogram_image,
HuffmanTreeCode* const huffman_codes) {

4
src/webp/encode.h
View File

@ -69,7 +69,9 @@ WEBP_EXTERN(size_t) WebPEncodeLosslessBGRA(const uint8_t* bgra,
typedef enum {
WEBP_HINT_DEFAULT = 0, // default preset.
WEBP_HINT_PICTURE, // digital picture, like portrait, inner shot
WEBP_HINT_PHOTO // outdoor photograph, with natural lighting
WEBP_HINT_PHOTO, // outdoor photograph, with natural lighting
WEBP_HINT_GRAPH, // Discrete tone image (graph, map-tile etc).
WEBP_HINT_LAST
} WebPImageHint;
typedef struct {