JPEG XL

jxl-oxide works quite nicely with the --allow_partial_files option. For small (~64kB) JXL images I'm personally not able to get anything less than 50% of the original size to be decoded, I'm assuming the lowest quality layer will always be some 20-30kB at least, regardless of full image size?

I don't recall my results from testing a few months ago, but it might be easier just sending the first 30kB of files via a 206 partial content http request. It's the same method used to buffer videos without loading the entire file

Alright. This is a project with high power usage constraints so we want to send the least amount of bytes for the thumbnail/preview. I'm assuming there's a concrete number of bytes that compose the minimum preview image, but currently the libjxl encoder does not in any way output this number? Will have to look into modifying the source.

`jxl-oxide -I --all-frames --with-offset` will tell you the position of the different components inside the JXL file. If I recall, LFGlobal is the minimum needed to preview

An idea previously discussed was making an index listing preview sizes for the server to reference when the file is requested, if you don't mind some extra work server side

🤦‍♂️ I was using libjxl tools instead of jxl-oxide. Ofc ofc. That command helps a lot! Thanks for the lead.

There's a lot of promise with the format, but right now you need to know how to coax it into doing what you want haha

<@306129091931668483> Something I didn't mention is the Table Of Contents, which does include the LFGlobal and it's size in the header of the file. But I think you need to decode the header yourself if you want to use it currently, hence pointing at Oxide first

F.3 in the spec, which you can find a draft version of here https://discord.com/channels/794206087879852103/1021189485960114198/1256224842894540831

Isn't there a way to ask libjxl for the lqip?