Added is_lossless to WebPImageFile#9602
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ajslater wants to merge 3 commits intopython-pillow:mainfrom
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There's possibly a general case for an "is_lossless" property on many or all Image formats. |
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Could you elaborate on this? If we did go with your suggestion, I think it would be better as another key in |
radarhere
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May 2, 2026
| def _is_lossless(data: bytes) -> bool: | ||
| # A WebP file is considered lossless when every coded frame uses the | ||
| # VP8L bitstream. See https://developers.google.com/speed/webp/docs/riff_container | ||
| if len(data) < 16 or data[:4] != b"RIFF" or data[8:12] != b"WEBP": |
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| if len(data) < 16 or data[:4] != b"RIFF" or data[8:12] != b"WEBP": | |
| if not _accept(data): |
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I find it useful to know if a WebP Image was encoded with the lossless bit set. While the exact amount of true 'losslessness' in encoded images can be a contentious subject, i find knowing the encoder's intent useful.
This sets the is_lossless property to true if every frame of the WebP was encoded with the lossless bit set. A simple determination for single frame images, but a restrictive judgement call for animated WebP's which main contain a mix of frame types.
Tell me if this looks useful and I can modify this PR to work well as a Pillow contribution.