dany/libwebp
1
0
Fork 0
mirror of https://github.com/webmproject/libwebp.git synced 2025-07-12 22:14:29 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity

add a -dither dithering option to the decoder

Browse Source 
Even at high quality setting, the U/V quantizer step is limited
to 4 which can lead to banding on gradient.
This option allows to selectively apply some randomness to
potentially flattened-out U/V blocks and attenuate the banding.

This option is off by default in 'dwebp', but set to -dither 50
by default in 'vwebp'.

Note: depending on the number of blocks selectively dithered,
we can have up to a 10% slow-down in decoding speed it seems.

Change-Id: Icc2446007f33ddacb60b3a80a9e63f2d5ad162de
This commit is contained in:
skal
2013-11-26 22:59:02 +01:00
committed by Pascal Massimino
parent e812401299
commit cbdd3e6e53
11 changed files with 138 additions and 11 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
examples/vwebp.c
View File

@ -376,6 +376,7 @@ static void Help(void) {
" -noicc ....... don't use the icc profile if present.\n"
" -nofancy ..... don't use the fancy YUV420 upscaler.\n"
" -nofilter .... disable in-loop filtering.\n"
" -dither <int> dithering strength (0..100). Default=50.\n"
" -mt .......... use multi-threading.\n"
" -info ........ print info.\n"
" -h ....... this help message.\n"
@ -397,6 +398,7 @@ int main(int argc, char *argv[]) {
fprintf(stderr, "Library version mismatch!\n");
return -1;
}
config->options.dithering_strength = 50;
kParams.use_color_profile = 1;
for (c = 1; c < argc; ++c) {
@ -409,6 +411,8 @@ int main(int argc, char *argv[]) {
config->options.no_fancy_upsampling = 1;
} else if (!strcmp(argv[c], "-nofilter")) {
config->options.bypass_filtering = 1;
} else if (!strcmp(argv[c], "-dither") && c + 1 < argc) {
config->options.dithering_strength = strtol(argv[++c], NULL, 0);
} else if (!strcmp(argv[c], "-info")) {
kParams.print_info = 1;
} else if (!strcmp(argv[c], "-version")) {