But usually there's a step after it called residual coding, where you subtract the predicted image from the original and send the difference to make up for errors. Just leaving that out is, um, interesting.
Obviously because it would make the file bigger if that was included...
The concept behind JBIG2 is good - small variations and random pixels are likely to be scanner noise/dust, so suppressing them can reduce filesize significantly. The problem here is that some JBIG2 implementations can be too lossy, and throw away the few pixels that could make all the difference between e.g. a 6 or an 8.
Obviously because it would make the file bigger if that was included...
The concept behind JBIG2 is good - small variations and random pixels are likely to be scanner noise/dust, so suppressing them can reduce filesize significantly. The problem here is that some JBIG2 implementations can be too lossy, and throw away the few pixels that could make all the difference between e.g. a 6 or an 8.