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gif2webp: force low duration frames to 100ms

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this is consistent with web browser behavior as well as various
transcoding tools (ffmpeg, gif2apng, etc).

also: update anim_diff to account for this new behaviour.

BUG=webp:379

Change-Id: I70cc72a6b401ef32b73cd182a3f12d993d495bf4
This commit is contained in:
James Zern 2018-03-23 22:48:17 -07:00 committed by Pascal Massimino
parent b2db361ca6
commit 09333097ed
2 changed files with 11 additions and 0 deletions
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3
examples/anim_util.c
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@ -593,6 +593,9 @@ static int ReadAnimatedGIF(const char filename[], AnimatedImage* const image,
curr_frame = &image->frames[i];
curr_rgba = curr_frame->rgba;
curr_frame->duration = GetFrameDurationGIF(gif, i);
// Force frames with a small or no duration to 100ms to be consistent
// with web browsers and other transcoding tools (like gif2webp itself).
if (curr_frame->duration <= 10) curr_frame->duration = 100;
if (i == 0) { // Initialize as transparent.
curr_frame->is_key_frame = 1;

8
examples/gif2webp.c
View File

@ -361,6 +361,14 @@ int main(int argc, const char *argv[]) {
GIFDisposeFrame(orig_dispose, &gif_rect, &prev_canvas, &curr_canvas);
GIFCopyPixels(&curr_canvas, &prev_canvas);
// Force frames with a small or no duration to 100ms to be consistent
// with web browsers and other transcoding tools. This also avoids
// incorrect durations between frames when padding frames are
// discarded.
if (frame_duration <= 10) {
frame_duration = 100;
}
// Update timestamp (for next frame).
frame_timestamp += frame_duration;