For our research, we need to detect a dent in a coca cola can. We tried to crop the picture so we can see the region we want to detect in. However the cropping part does not work in our advantage. In this research we need to know wether the dent in the can is more than 4mm. We had the idea to detect it by using a local minimum. This did not work as well. We desperately need your help. The code and our test image are provided in this message. The first picture is the complete image, and the second picture is the desired cropped image.