Image Processing: How to detect borders of a bill in an image

Question

I'm working on Python 2.7, using the OpenCV library. I am trying to find automatically make the edges of the bill and to crop it at the right (rectangular) size, here is one example:

Answer 1

What you have asked is too general and difficult to do it perfectly (Due to curved edges , and bad white balance in the picture). The basic try in edge detection can be done with Canny Edge detection.

But the bill does not have exact rectangular edge , and the paper is bent. The best way you can develop a solution is to make a Camscanner like application , which uses OpenCV in it.