introduce a generic WebPPictureHasTransparency() function

VP8-lossy will now avoid writing an ALPH chunk if the
alpha values are trivial.

+ changed DumpPicture() accordingly in cwebp
+ prevented the -d option to be active with lossless
 (DumpPicture wouldn't work).

Change-Id: I34fdb108a2b6207e93fa6cd00b1d2509a8e1dc4b
This commit is contained in:
Pascal Massimino
2012-06-04 15:50:05 -07:00
parent d2b6c6c03b
commit 437999fb77
5 changed files with 41 additions and 13 deletions

View File

@ -650,7 +650,8 @@ static int DumpPicture(const WebPPicture* const picture, const char* PGM_name) {
const int uv_width = (picture->width + 1) / 2;
const int uv_height = (picture->height + 1) / 2;
const int stride = (picture->width + 1) & ~1;
const int alpha_height = picture->a ? picture->height : 0;
const int alpha_height =
WebPPictureHasTransparency(picture) ? picture->height : 0;
const int height = picture->height + uv_height + alpha_height;
FILE* const f = fopen(PGM_name, "wb");
if (f == NULL) return 0;
@ -1035,7 +1036,11 @@ int main(int argc, const char *argv[]) {
// Write info
if (dump_file) {
DumpPicture(&picture, dump_file);
if (picture.use_argb_input) {
fprintf(stderr, "Warning: can't dump file (-d option) in lossless mode.");
} else if (!DumpPicture(&picture, dump_file)) {
fprintf(stderr, "Warning, couldn't dump picture %s\n", dump_file);
}
}
if (!quiet) {