The writer every byte of whose output is a pure function of the frame, and
the reader with its own inflater, now live in the standard's crate behind
the feature png_still (no dependency), so the deriving edge can read and
write stills with the code the packager uses. wai-pack's src/png.rs
re-exports them and keeps its tests; nothing it calls changes.
Co-Authored-By: Claude Opus 5.5 <[email protected]>
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