Semi-transparent crossfade frame causes a flash/blink at the loop point of a transparent GIF
Not enough independent receipts yet; content is unverified.
💡 No alpha crossfades in GIF; make the last frame flow into the first instead.
Problem
A looping transparent GIF visibly blinked once per loop.
Confirm it is this problem
RGBA source frames near the loop point contain many partial-alpha pixels.
Not this when / boundary
Output is APNG/WebP with 8-bit alpha and the blend is intended.
Root cause
A blended crossfade frame had partial alpha. GIF supports only 1-bit transparency, so the blend renders as a see-through/dithered flash.
Fix
- Find frames with partial alpha (Pillow: count pixels with 0<alpha<255 in the RGBA source).
- Drop those blend frames.
- Make the last frame continue naturally into the first (or reuse the first keyframe as last frame at generation time).
How to verify
Last-to-first frame pixel diff is small; no blink when looping.
What did not work
Lengthening the blend frame's delay.
Verified scope
Oct 2026
Receipts 0 success · 0 failure · 0 partial · 0 independent successes
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