fix(build): ship libwebpdemux2 so pi3 Pillow can save WebP - #3042
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The upload image-normalisation pipeline converts HEIC/HEIF/TIFF/etc. to lossless WebP via Pillow. On 32-bit Pi (armv7) there's no Pillow wheel, so it's compiled from source against libwebp-dev and dynamically links the whole webp family at runtime: libwebp7, libwebpmux3 *and* libwebpdemux2 (Pillow's _webp uses WebPAnimDecoder). The runtime image only pulled libwebp7 + libwebpmux3 — both transitive deps of ffmpeg's libavcodec — but NOT libwebpdemux2, which nothing else depends on. Without it, ``import PIL._webp`` fails to resolve libwebpdemux.so.2, the WebP plugin registers no save handler, and the conversion dies with ``KeyError: 'WEBP'`` (Sentry ANTHIAS-1Y, 11 events, all pi3). Add libwebp7 / libwebpdemux2 / libwebpmux3 to the runtime base_apt_dependencies explicitly so the pipeline never depends on ffmpeg's transitive graph — same rationale as the libheif1 entry beside them. Inert on 64-bit boards (their Pillow wheel bundles its own webp libs), so listed unconditionally for simplicity, matching libheif1. Verified: a from-source Pillow 12.2.0 _webp.so on debian:trixie links libwebp.so.7, libwebpmux.so.3, libwebpdemux.so.2 and libsharpyuv.so.0; installing ffmpeg+libheif1 leaves libwebpdemux2 absent. Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>
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Pull request overview
This PR fixes runtime WebP support for Pillow on 32-bit Raspberry Pi (armv7) by ensuring the Anthias runtime image includes the full set of required libwebp shared libraries (including libwebpdemux.so.2), preventing PIL._webp import/link failures that lead to KeyError: 'WEBP' during image normalization.
Changes:
- Add explicit runtime APT deps for Pillow WebP support:
libwebp7,libwebpdemux2,libwebpmux3. - Document why these are needed (armv7 builds Pillow from source; ffmpeg does not pull
libwebpdemux2transitively).
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What
The upload image-normalisation pipeline converts HEIC/HEIF/TIFF/etc. to lossless WebP via Pillow. On 32-bit Pi (armv7) there's no Pillow wheel, so it's compiled from source against
libwebp-devand dynamically links the whole webp family at runtime.The runtime image only carried
libwebp7+libwebpmux3(both transitive deps offfmpeg'slibavcodec) — but notlibwebpdemux2, which nothing else pulls. Without it,import PIL._webpcan't resolvelibwebpdemux.so.2, the WebP plugin registers no save handler, and the conversion dies withKeyError: 'WEBP'(Sentry ANTHIAS-1Y, 11 events, allpi3).Fix
Add
libwebp7/libwebpdemux2/libwebpmux3to the runtimebase_apt_dependenciesexplicitly so the pipeline never depends on ffmpeg's transitive graph — same rationale as thelibheif1entry beside them. Inert on 64-bit boards (their Pillow wheel bundles its own webp libs), so listed unconditionally for simplicity, matchinglibheif1.Verification
On
debian:trixie, a from-sourcePillow==12.2.0_webp.solinks:Installing only
ffmpeg+libheif1(runtime parity) leaveslibwebpdemux2absent while the other three are present — exactly the failure signature. GeneratedDockerfile.serverforpi3now installs all three at runtime alongsidelibheif1.🤖 Generated with Claude Code