This is pretty sweet. I wonder if this is better than running pdf.js.

I just recently needed jbig2 image support in my web app and using pdf.js wasn't gonna work and be too slow and the wrong interface anyway, so I took the source code for the jbig2 decoder and vibe coded a converter that outputs 1 bit pngs. After some manual culling of code I got the wasm module down to 27kb with no glue.