If you like taking photos, then you will probably also find yourself cropping your photos from time to time. I will crop photos to get rid of background noise or to just focus more on the subject I was trying to capture. I also like to take high-resolution photos of insects or other small creatures and then crop it down to make it seem like I was even closer to the insect than I really was.
Now, most people will use a photo editing application to crop their image, such as Photoshop Elements. I use these kinds of tools too, but you can also use the Python programming language to do the cropping for you. One good example where you might want to use Python is if you have thousands of scanned images of the same type, then it makes more sense to just write a script to do the cropping for you.