Jpeg->Avif color changed #4720
Replies: 3 comments 2 replies
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Hi @zhifengzhuang, your avifenc output is 10-bit, perhaps your mac is displaying it differently. Do you have an HDR screen? If I make 8-bit AVIF and compare to your jpg I see: So the average difference is small. Running |
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Hi @jcupitt. Yes, when I use vips copy, the result is the same. I noticed that the default effort parameter for vips heifsave is 4. When I set the effort to 2, the outcome changes. |
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You're right!
Original, You can see the difference image has quite a strong blue cast. I suppose the solution is to avoid low effort conversion. This seems like an aom issue. |
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As far as I know, the "speed" parameter in libavif corresponds to "cpu_used" in libaom, while the "effort" in libvips is equivalent to 9 minus cpu_used. This means: using avifenc with speed=7 is equivalent to using libvips with effort=2. I found that after setting subsample_mode to 'off', the color variation becomes minimal. Upon checking, I learned that libvips uses yuv444 when subsample_mode=off. As for avifenc, it defaults to yuv444 if not explicitly set. However, libvips defaults to 'auto' mode and uses yuv420 when Q<90. If I explicitly set avifenc to yuv420, significant color changes occur as well. |
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Oh, interesting! Chroma subsample mode should not affect average colour, of course, I wonder if avifenc has a bug in rounding? |
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When converting JPEG to AVIF using libvips, the colors are changing. The command used is as follows.
vips heifsave origin.jpeg vips-10.avif --effort=2 --bitdepth=10 --compression=av1 --encoder=aomOrigin image is:
Avif result is:
vips-10.avif.zip
However, when I use avifenc, the result is normal. Unlike the grayish tint produced by vips after AVIF conversion, avifenc's output maintains the original image's predominantly green tone.
avifenc -c aom -q 50 --depth 10 --speed 7 origin.png avifenc-10.avifvips & avifenc version is:
Both run on my mac.
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