Sheet-feed scanners

Tom Jennings wrote: While I very much appreciate the stuff you've put online, I respectfully disagree with your "reproduced detail OK", at least in the general case. For text and line art, JPEG *completely* sucks. It makes the text and line art blurry. JPEG was intended for continuous-tone images, and throws away high-frequency content. And guess what. Text and line art have a LOT of high-frequency content. That's why it blurs them. For text and line art, lossless bilevel compression such as ITU T.4 and T.6 compression (known as Fax Group 3 and Group 4) are much better, as are JBIG and JBIG2. G3 and G4 can be packaged in TIFF files. G3, G4, and JBIG can be packaged in PDF files. JBIG and JBIG2 have slightly better compression than G4, but they are patented so I avoid them. G4 works quite well. For pages that contain ONLY text and line art, there is literally NO advantage to JPEG compression. It yields less compression and worse results. The thing that's really annoying when processing scanned documents is dealing with pages that have a mix of text or line art and continuous tone images. Although using JPEG for such pages is not optimal, it is certainly the path of least resistance, so I don't complain about it. A better solution (but much more difficult and/or time-consuming) is to composite the final page image from a G4 image of the text and line art and JPEG of the image(s). However, there are no freely available tools to do this, and I'm not even aware of anything commercial that can do this automatically. I've experimented some with putting support for this form of compositing in my "tumble" program, but without software to automatically identify the images, it would still be very time-consuming. Eric