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gif2webp: Add a mixed compression mode

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When '-mixed' option is given, each frame would be heuristically chosen
to be
encoded using lossy or lossless compression.

The heuristic is based on the number of colors in the image:
- If num_colors <= 31, pick lossless compression
- If num_colors >= 194, pick lossy compression
- Otherwise, try both and pick the one that compresses better.

Change-Id: I908c73493ddc38e8db35b7b1959300569e6d3a97
This commit is contained in:
Urvang Joshi
2013-11-17 18:04:07 -08:00
parent 87cffcc3c9
commit 73f52133a1
4 changed files with 167 additions and 41 deletions
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8
examples/gif2webp.c
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@ -212,6 +212,8 @@ static void Help(void) {
printf("options:\n");
printf(" -h / -help ............ this help\n");
printf(" -lossy ................. Encode image using lossy compression.\n");
printf(" -mixed ................. For each frame in the image, pick lossy\n"
" or lossless compression heuristically.\n");
printf(" -q <float> ............. quality factor (0:small..100:big)\n");
printf(" -m <int> ............... compression method (0=fast, 6=slowest)\n");
printf(" -kmin <int> ............ Min distance between key frames\n");
@ -253,6 +255,7 @@ int main(int argc, const char *argv[]) {
int default_kmax = 1;
size_t kmin = 0;
size_t kmax = 0;
int allow_mixed = 0; // If true, each frame can be lossy or lossless.
memset(&info, 0, sizeof(info));
info.id = WEBP_CHUNK_ANMF;
@ -279,6 +282,9 @@ int main(int argc, const char *argv[]) {
out_file = argv[++c];
} else if (!strcmp(argv[c], "-lossy")) {
config.lossless = 0;
} else if (!strcmp(argv[c], "-mixed")) {
allow_mixed = 1;
config.lossless = 0;
} else if (!strcmp(argv[c], "-q") && c < argc - 1) {
config.quality = (float)strtod(argv[++c], NULL);
} else if (!strcmp(argv[c], "-m") && c < argc - 1) {
@ -348,7 +354,7 @@ int main(int argc, const char *argv[]) {
if (!WebPPictureAlloc(&frame)) goto End;
// Initialize cache
cache = WebPFrameCacheNew(frame.width, frame.height, kmin, kmax);
cache = WebPFrameCacheNew(frame.width, frame.height, kmin, kmax, allow_mixed);
if (cache == NULL) goto End;
mux = WebPMuxNew();