Since I don't have a copier or scanner, I'm using an 8 megapixel camera to copy documents. This works pretty well except they need a lot of processing afterward. I'd like to get from a photo to a bitmap, but using
djpeg -grayscale -pnm photo.jpg | pgmtopbm -threshold -value XXX
does not work so well, for two reasons:
It's hard to guess what XXX should be, and XXX is different for different photos.
Illumination varies, and sometimes a single threshold isn't what's right for the image.
How can I do better? The ideal solution will be fully automatic command-line program that I can run on Linux. (I have already written a program to remove dark pixels from the edges of images.)
NOTE: I really want a bitmap, that's just black and white pixels. No grayscale, no dithering.