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Comment by throw0101c

1 day ago

JPEG-XL can be a quick win since it is possible to do a transcode of all of your existing ('classic') JPEG files with zero (visual) losses in quality.

I always think of transcode and lossless as opposites. How is this achieved in this format?

  • It extracts the already quantized DCT coefficients and related data from the JPEG bitstream and re-encodes them with JPEG XL’s more efficient entropy coding and container,

    Think of it as zip compression that is specially designed for JPEG and putting the JPEG data in a different/better container.

If you're transcoding why wont you go to avif or another one? If jpeg -> jpeg-xl uniquely better?

  • JPEG is a lossy format. JPEG -> AVIF adds a second loss operation. JPEG to JPEG-XL is lossless but with a smaller file size. So one does not further degrade the jpegs beyond what they were already degraded in creating them in the first place.

  • It's a lossless conversion while still saving spaces. You can even convert back to get the exact same file bit-perfect