Comment by doodlesdev
24 days ago
I knew about the lossless JPEG to JPEG XL compression story before, but had no idea that it was a two-way road. That's truly f* impressive. Boggles my mind even more the fact this format hasn't been adopted widely yet.
JPEG is a lossy frequency-space compression stage followed by a lossless Huffman coding stage. The second stage is quite generic as such, essentially compressing a stream of bits.
So you can relatively easily replace the second stage with something better. And since it's lossless you can easily go back.
Dropbox[1] and others have exploited this for reducing storage requirements, converting back on-demand so the client doesn't notice.
https://github.com/dropbox/lepton
byte-for-byte identical file actually. Not just imagery. You can basically save 30% without loosing ANY bit of the original file
Because what you save in terms of storage, you pay for in decode time, which is an important consideration on the web.
Do you? I just tried it locally, and decoding a 4.9MB, 6000×4000 JPEG with djpeg took about 400ms; decoding its losslessly-recompressed JXL (4.15MB) single-threaded with djxl took 300ms.
Cool. You're getting different results to everyone else. Do you see the same on https://random-stuff.jakearchibald.com/apps/img-decode-bench... (make sure you use a browser that supports JPEG XL)?
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I guess my surprise is mostly that it hasn't been adopted elsewhere. For instance, it still boggles my mind I can't store my JPEG XL images on Google Photos nor take photos as JPEG XL images directly on my Samsung smartphone, but can use HEIC for some fruity reason.
Google Photo teams wanted JXL too, but had to hold back due to Chromium not supporting them
The DoS thing would certainly make me worry about handling these images on my server.
You pay for decoding only when you view the image, whereas storage is a persistent cost.