In particular for converting scanned documents to black and white. Though you can get nicer results with grayscale.

This library might have saved me a lot of time recently, as I don't have a working scanner and was forced to photograph and clean up a lot of pages of documents. I used gimp, which required a lot of experimentation. It's only got a couple adaptive tools that can do the job with uneven lighting, but they sometimes require some pre or post processing for good results.

Yes, or OCR