Preview.app’s signature capture system

I love how MacOS’ PDF viewer has the ability to add images of signatures to documents. I’ve been signing a lot of forms with it lately and it’s great.

The capture algorithm is interesting. Here’s a “signature” it generated when it had a view of the other side of my office, with a desk and a bunch of crap piled on it. Heavy edge detection! The cylinder just to left of center is a metal water bottle; can also see some electronic equipment (the box on left) and standing file folders (right).