How to know that if the only visible area of a .png is touched in Xcode

Question

I have imported a .png image into UIImageView in Xcode and what I want to make is when the image is touched, it will be hidden.

But my problem is that

Answer 1

I have taken the liberty of updating 'Danny S's' answer to Swift 5 and removed extraneous code, bug fixed and added some additional clarity to the UX.

Here's the code:

https://github.com/ZoeESummers/SOXShapedTapView-Updated.git