Guix

JBIG2 is designed for lossy or lossless encoding of bilevel (1-bit monochrome) images at moderately high resolution, and in particular scanned paper documents. In this domain it is very efficient, offering compression ratios on the order of 100:1.

This is a decoder only implementation, and currently is in the alpha stage, meaning it doesn't completely work yet. However, it is maintaining parity with available encoders, so it is useful for real work.