[ownedbycats]

Originally Posted by ownedbycats

I seem to vaguely recall something about Internet Archive using some sort of proprietary compression tech, but I'm having a hard time trying to pull enough details from my memory to be able to actually find anything on it - it's possible I might've posted before about it so I'll look.

Found it.

Originally Posted by ownedbycats

Yes, I've seen the invisible text layer on some PDFs from other sources. From what I recall, the Internet Archive uses LuraTech's brand of mixed-raster content compression. Basically there's several different images and the text all layered on each page. It's pretty efficient in filesize, but slow to render and can look pretty terrible if done poorly.