I have a hobby-project where I collect stickered Laptop-Lids [1], and since I get most photos from twitter or by mail, they are often not centered and straight, but somehow skewed. I made a small MacOS-App [2] with Swift that allows me to click on the laptops corners, and export a cropped image (using CIPerspectiveCorrection). Photoshop has this exact feature under "perspective crop", but I wanted to do some Mac-Dev and save some time by not having to boot PS.
[1] https://devlids.com [2] https://github.com/niorad/Skewbacca-Native