Comment by adzm
2 days ago
JPEG transcoding is one of the neatest features of JXL; there is so much existing jpeg out there. Eventually that may be unnecessary, but it's looking like this could already save a significant amount of space for photo archive backups for example.
That's just by changing the entropy coder and retaining the DCT coefficients. The idea is similar to Dropbox's Lepton. https://dropbox.tech/infrastructure/lepton-image-compression...
The main difference being that Lepton is worse and 100x slower.
Lepton guarantees that JPEG->Lepton->JPEG produces an identical file, not just identical pixels. Does JPEG XL achieve the same thing?
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The blog post is from 10 years ago. I'm sure it's much faster on modern hardware. I'd say that the main difference is that JPEG XL can be rendered directly in many applications, while Lepton files will have to be processed into JPEG out of your archives.
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