Fixes #331.
"Compress image before uploading" re-encodes through a canvas to JPEG, and only PNG was skipped:
- a **transparent WebP** (sticker, logo) came out with a **black** background;
- an **animated GIF or WebP** became a **single still frame**.
**Change**
- `isCompressible` no longer offers `image/gif` or `image/apng`.
- `compressImage` returns `null` (upload the original) for an **animated WebP**, detected by the VP8X header's animation flag.
- It also returns `null` for any image with a **transparent pixel**, checked on the canvas before encoding.
- Opaque JPEG and WebP still compress as before.
**Verified** with the real `compressImage` in Chromium, using 64×64 WebPs made on a canvas:
- transparent → **kept original**;
- opaque → `image/jpeg`;
- `isCompressible('image/gif')` → `false`.
Unit tests for `isAnimatedWebp` and `hasTransparency`. The existing GIF-compressible assertion is updated, since that behaviour changes on purpose.
`tsc` clean · ESLint clean.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
https://claude.ai/code/session_017PCb59uY3UKqDqt7B6hzd5
Compression re-encodes through a canvas to JPEG. Only PNG was skipped,
so a transparent WebP came out on a black background, and an animated
GIF or WebP became one still frame. GIF and APNG are no longer offered;
an animated WebP (VP8X animation flag) or any image with a transparent
pixel is kept as the original.
Fixes#331
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017PCb59uY3UKqDqt7B6hzd5
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Fixes #331.
"Compress image before uploading" re-encodes through a canvas to JPEG, and only PNG was skipped:
Change
isCompressibleno longer offersimage/giforimage/apng.compressImagereturnsnull(upload the original) for an animated WebP, detected by the VP8X header's animation flag.nullfor any image with a transparent pixel, checked on the canvas before encoding.Verified with the real
compressImagein Chromium, using 64×64 WebPs made on a canvas:image/jpeg;isCompressible('image/gif')→false.Unit tests for
isAnimatedWebpandhasTransparency. The existing GIF-compressible assertion is updated, since that behaviour changes on purpose.tscclean · ESLint clean.🤖 Generated with Claude Code
https://claude.ai/code/session_017PCb59uY3UKqDqt7B6hzd5