And if you already have compression artifacts, what use is lossless?
Only time you would want it is when you are uploading comparison photos specifically showing compression artifacts created from some other compression result.
That's a bit to niche to make it worthwhile.

[–] GamingChairModel@lemmy.world 2 points 1 day ago (1 children)

And if you already have compression artifacts, what use is lossless?

To further reduce file size without further reducing quality.

There are probably billions of jpeg files out there in the world already encoded in lossy JPEG, with no corresponding higher quality version actually available (e.g., the camera that captures the image and immediately saves it as JPEG). We shouldn't simply accept that those file sizes are going to forever be stuck, and can think through codecs that further compress the file size losslessly from there.

[–] ulterno@programming.dev 0 points 1 day ago (1 children)

Wait, so lossless webp manages to be smaller than even lossy jpg, while also having to losslessly reproduce jpeg artifacts, which tends to otherwise greatly increase file sizes (as compared to the original lossless file) in lossless formats?

[–] GamingChairModel@lemmy.world 2 points 1 day ago

JPEG XL has a mode for losslessly encoding any lossy JPEG into a smaller file size without any loss of quality. Wikipedia has some description of general approaches for losslessly encoding JPEG files further.

I don't know if webp uses any of these tricks, but I don't see why it would be hard to imagine that compression artifacts from a 30-year-old format can be encoded more efficiently today.