Support animated profile pictures with improved image handling

[retrixe]

I think we really want to offload this conversion step to some tool like magick and store as AVIF

The current solution with nativewebp really doesn't work well, lol

[retrixe]

For animated images, this seems to work: https://github.com/AOMediaCodec/libavif/wiki/Sequences

[retrixe]

The latest commit 466f9cb uses AVIF encoding, GIF/APNG support is pending

[retrixe]

On second thought, do we even want animated profile pictures? It seems distracting to have in chat...

Frontend handling of such images will need to avoid autoplay. We could support ingesting GIFs maybe? Well, I won't retract this issue, there's other things in image handling to improve!

6cca667 stores images losslessly on the backend (overkill, but well, I'm weird like that...)

I'm planning to explore JPEG XL this week for storing images, and converting them to AVIF upon retrieval. JXL seems to decode much faster than AVIF does, which makes it great for storage purposes, and the resulting images are smaller too. The only cost is more expensive encode (for lossless JXL), and added conversions when retrieving 4096 size images.

I also want to explore ImageMagick for ingesting images, though we probably won't leverage it for retrieval yet, since I can't figure out what avifenc quality values correspond to in ImageMagick... If we do this, we'll probably be using lossless AVIF or JXL for storage.

[retrixe]

225e61b switches away from AVIF lossless, storing with avifenc -q 85 instead:

• If we're going to change image formats down the line, it'll be in, like, 20 years, so why save lossless? JPEG XL in browsers doesn't seem any closer and it doesn't seem like it's immediately worth switching to JXL anyway.
• For 256x256 previews in chat, a second encode pass is perfectly fine.
• I don't want to rework the code to save PNG or JPEG XL right now (objectively better formats for lossless, but otherwise, not good for serving to end users).

bff33f2 brings some minor refactoring to the source code, and a4b861c 098e43f 5b8ebef enable ingesting WebP, TIFF, BMP, GIF and AVIF images (not animated though!)

Frankly, the best way to handle this would be to outsource this work to a CDN or other dedicated optimisation service that's already figured out the math...