New Post: Crop Image only Scanned Area

I want to crop image only the scanned area. For example, I setup scanner to 8 x 11 paper size setting and scanned a 4 X 5 document. It created an image according to 8 x 11 paper size image. Now I want to crop only 4 X 5 area and save to a new image. Any C# coding help will be very much appreciated.

Best Regards,
Ahmed