This feels like the wrong end to optimize. Zip is plenty of fast, especially when it comes to a few hundred pages of a comic. Meanwhile the image decoding can take a while when you want to have a quick thumbnail overview showing all those hundred pages at once. No comic/ebook software I have ever touched as managed to match the responsiveness of an actual book where you can flip through those hundreds of pages in a second with zero loading time, despite it being somewhat trivial to implement when you generate the necessary thumbnail/image-pyramid data first.A multi-resolution image format would make more sense than optimizing the archive format. There would also be room for additional features like multi-language support, searchable text, … that the current "jpg in a zip" doesn't handle (though one might end up reinventing DJVU here).
fc417fc802|1 month ago
There are already quite a few cbz archives in the wild that contain jxl encoded images. That's a multi-resolution format at least to the extent that it supports progressive decoding at fixed levels that range from 1:8 to as high as 1:4096. I think it might also support other arbitrary ratios subject to certain encoding constraints but I'm less clear on that.
Readers might need to be updated to make use of the feature in an intelligent manner though. The jxl cbzs I've encountered either didn't make use of progressive encoding or else the software I used failed to take advantage of it - I'm not sure which.