feat: add animated WebP encoding and decoding support#103
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Encoder:
- encodeAnimated(frames, options) accepts array of {imageData, duration}
and produces animated WebP with infinite loop via WebPAnimEncoder API
- Links against libwebpmux for muxing frames into container
Decoder:
- decode(buffer) now handles both static and animated WebP (falls back
to demux API for animated files, returning first composited frame)
- decodeAnimated(buffer) returns array of {imageData, duration} frames
with proper alpha blending and disposal method handling
- isAnimated(buffer) returns boolean
- Links against libwebpdemux for demuxing animated WebP
Also upgrades EMSDK from 2.0.34 to 3.1.57 to fix terser minifier crash.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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This was referenced Mar 31, 2026
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## Summary - Extends client-side image optimization to convert **JXL → JPEG**, **HEIC → JPEG**, and **animated GIF → animated WEBP** using jSquash WASM packages before upload - Transparent JXL/HEIC images are converted to **WEBP** instead of JPEG, so transparency is preserved (WEBP compresses much better than PNG for this case) - Gated as an **upcoming change** via `composer_media_optimization_image_convert_enabled` (experimental, `feature,all_members`, opt-in per group through the upcoming changes admin UI) - Sends raw file bytes to Web Worker for formats browsers can't decode natively (JXL, HEIC), with new `"convert"` and `"convertAnimated"` worker message types - Adds JXL to `authorized_extensions` and `supported_images`; adds HEIC/HEIF to `supported_images` for consistency - Skips GIF→WEBP when output is larger than input - Falls back to filename when MIME type is missing (browsers may not recognize JXL/HEIC) ### Note on jSquash packages This depends on Discourse-scoped forks of the jSquash packages (`@discourse/jxl`, `@discourse/heic`, `@discourse/webp`, `@discourse/gif`, `@discourse/jpeg`, `@discourse/resize`). The following upstream PRs would let us move back to the canonical `@jsquash/*` packages, but the upstream maintainer is currently unresponsive: - jamsinclair/jSquash#101 (`@jsquash/heic`) - jamsinclair/jSquash#103 (`@jsquash/webp` animated support) - jamsinclair/jSquash#104 (`@jsquash/gif`) --------- Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Encoder:
Decoder:
Also upgrades EMSDK from 2.0.34 to 3.1.57 to fix terser minifier crash.