[komatsu]

Otsu's method finds a single threshold value in an adaptive way. This can't solve a scanned document thresholding problem.

btw: The iOS Notes app has quite a capable document scanning tool. It's cleverly hidden though.

[Rygian]

I'm pretty happy with the scanning feature of Evernote, and I think there are some other nice apps in the Android app store, but my goal is to have a solution that is not captive (either to a specific vendor or to a SaaS solution).