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Note that AVIF is badly broken on the stable version of Gimp (2.10.34). Chroma is upscaled using NEAREST NEIGHBOR. Gimp does not do that when you load a JPEG
by Dwedit 3y ago
Note that AVIF is badly broken on the stable version of Gimp (2.10.34). Chroma is upscaled using NEAREST NEIGHBOR. Gimp does not do that when you load a JPEG or other lossy file which uses chroma subsampling.
- pornel 3y agoSadly, upsampling algorithm in AVIF has been explicitly left unspecified, because the video industry doesn't see a problem with that. IMO using chroma subsampling with AVIF is always an error. That mode shouldn't exist, and it's there only due to video legacy. Just always use full-res color. AV1 has chroma-from-luma feature to deal with full-res chroma efficiently. If you destroy color resolution like it's 1953, you're just degrading both the quality and the compression for no good reason.
- JyrkiAlakuijala 3y agoI tried to keep it away from pik (successfully) and jpeg xl (with moderate success), but in the end we needed to add yuv420/yuv422 for old school jpeg recompression (75 % of old jpegs are in this unfortunate mode). Usual JPEG XL images are always yuv444.