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gif2webp: fix transcode of loop count=65535

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with loop_compatibility disabled (the default), non-zero loop counts
will be incremented by 1 for browser rendering compatibility. the max,
65535, is a special case as the muxer will fail if it is exceeded; avoid
increasing the limit in this case. this isn't 100% correct, but should
be close enough given the high number of iterations.

BUG=webp:382

Change-Id: Icde3e98a58e9ee89604a72fafda30ab71060dec5
This commit is contained in:
James Zern
2018-05-09 17:36:13 -07:00
parent dce5d76431
commit af0e4fbb06
4 changed files with 21 additions and 3 deletions
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14
examples/anim_diff.c
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@ -143,8 +143,18 @@ static int CompareAnimatedImagePair(const AnimatedImage* const img1,
if (!ok) return 0; // These are fatal failures, can't proceed.
if (is_multi_frame_image) { // Checks relevant for multi-frame images only.
ok = CompareValues(img1->loop_count, img2->loop_count,
"Loop count mismatch") && ok;
int max_loop_count_workaround = 0;
// Transcodes to webp increase the gif loop count by 1 for compatibility.
// When the gif has the maximum value the webp value will be off by one.
if ((img1->format == ANIM_GIF && img1->loop_count == 65536 &&
img2->format == ANIM_WEBP && img2->loop_count == 65535) ||
(img1->format == ANIM_WEBP && img1->loop_count == 65535 &&
img2->format == ANIM_GIF && img2->loop_count == 65536)) {
max_loop_count_workaround = 1;
}
ok = (max_loop_count_workaround ||
CompareValues(img1->loop_count, img2->loop_count,
"Loop count mismatch")) && ok;
ok = CompareBackgroundColor(img1->bgcolor, img2->bgcolor,
premultiply) && ok;
}