test: regression tests for small interlaced GIF decode failure#232
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lilith wants to merge 1 commit intoimage-rs:masterfrom
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test: regression tests for small interlaced GIF decode failure#232lilith wants to merge 1 commit intoimage-rs:masterfrom
lilith wants to merge 1 commit intoimage-rs:masterfrom
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Three valid interlaced GIFs (7x7, 9x9, 47x63) produced by gifsicle 1.95 are rejected with "image truncated". All decode correctly with giftopnm (netpbm) and are valid per the GIF89a spec. Root cause: when decoding interlaced frames, read_into_buffer passes per-row slices to the LZW decoder. For small images (7-47 byte rows), weezl's NoProgress status triggers two bugs in DecodeSubBlock: 1. Input data is skipped instead of retried with a smaller buffer 2. NoProgress during flush is treated as end-of-stream Related: image-rs/weezl#72
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Three valid interlaced GIFs produced by gifsicle 1.95 are rejected with "image truncated". All decode correctly with giftopnm (netpbm).
Root cause: when decoding interlaced frames,
read_into_bufferpasses per-row slices to the LZW decoder. For small images (7-47 byte rows), weezl returnsNoProgressbecause the output buffer is too small for its internal state machine to advance. The gif crate mishandles this by either skipping input data or treating it as end-of-stream.Related: image-rs/weezl#72
This PR adds only failing tests — no fix included. The three test GIFs are inlined as byte arrays (39-149 bytes each).