I was reminded how important documentation is today after spending fifteen minutes trying to figure out why a certain code path wasn’t being reached.

If you shuffle between UIImage, CIImage, and CGImage a lot, you might be tempted to access the handy “.ciImage” property of a UIImage. However, that property definitely does NOT have a value if you initialized your UIImage from a CGImage, and you need to use a CIImage initializer instead. Thanks, Apple docs!