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add a -z option to cwebp, and WebPConfigLosslessPreset() function

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These are presets for lossless coding, similar to zlib.
The shortcut for lossless coding is now, e.g.:
   cwebp -z 5 in.png -o out_lossless.webp

There are 10 possible values for -z parameter:
   0 (fastest, lowest compression)
to 9 (slowest, best compression)

A reasonable tradeoff is -z 6, e.g.
-z 9 can be quite slow, so use with care.

This -z option is just a shortcut for some pre-defined
'-lossless -m xx -q yy' combinations.

Change-Id: I6ae716456456aea065469c916c2d5ca4d6c6cf04
This commit is contained in:
skal
2014-03-11 23:25:35 +01:00
parent 30176619c6
commit 65b99f1c92
4 changed files with 54 additions and 2 deletions
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16
examples/cwebp.c
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@ -568,6 +568,8 @@ static void HelpLong(void) {
printf(" default, photo, picture,\n");
printf(" drawing, icon, text\n");
printf(" -preset must come first, as it overwrites other parameters.");
printf(" -z <int> ............... Activates lossless preset with given "
" level in [0:fast, ..., 9:slowest]\n");
printf("\n");
printf(" -m <int> ............... compression method (0=fast, 6=slowest)\n");
printf(" -segments <int> ........ number of segments to use (1..4)\n");
@ -672,6 +674,8 @@ int main(int argc, const char *argv[]) {
uint32_t background_color = 0xffffffu;
int crop = 0, crop_x = 0, crop_y = 0, crop_w = 0, crop_h = 0;
int resize_w = 0, resize_h = 0;
int lossless_preset = 6;
int use_lossless_preset = -1; // -1=unset, 0=don't use, 1=use it
int show_progress = 0;
int keep_metadata = 0;
int metadata_written = 0;
@ -726,8 +730,13 @@ int main(int argc, const char *argv[]) {
picture.height = strtol(argv[++c], NULL, 0);
} else if (!strcmp(argv[c], "-m") && c < argc - 1) {
config.method = strtol(argv[++c], NULL, 0);
use_lossless_preset = 0; // disable -z option
} else if (!strcmp(argv[c], "-q") && c < argc - 1) {
config.quality = (float)strtod(argv[++c], NULL);
use_lossless_preset = 0; // disable -z option
} else if (!strcmp(argv[c], "-z") && c < argc - 1) {
lossless_preset = strtol(argv[++c], NULL, 0);
if (use_lossless_preset != 0) use_lossless_preset = 1;
} else if (!strcmp(argv[c], "-alpha_q") && c < argc - 1) {
config.alpha_quality = strtol(argv[++c], NULL, 0);
} else if (!strcmp(argv[c], "-alpha_method") && c < argc - 1) {
@ -916,6 +925,13 @@ int main(int argc, const char *argv[]) {
goto Error;
}
if (use_lossless_preset == 1) {
if (!WebPConfigLosslessPreset(&config, lossless_preset)) {
fprintf(stderr, "Invalid lossless preset (-z %d)\n", lossless_preset);
goto Error;
}
}
// Check for unsupported command line options for lossless mode and log
// warning for such options.
if (!quiet && config.lossless == 1) {