Making deep copy of UIImage

Question

My class contains an UIImage property which I want to enforce as a \'copy\' property by any external clients accessing it. But, when I try to do a copy in my custom setter,

Answer 1

A deep copy

When talking about deep copies we must first understand that UIImage is a container. It doesn't actually contain the image data. The underlying data can be a CIImage or a CGImage. In most cases the backing data is a CGImage which is in turn a wrapping struct and copying the CGImage is just copying the metadata and not the underlying data. If you want to copy the underlying data you can draw the image into a context or grab a copy of the data as a PNG.

UIImagePNGRepresentation

Creating a playground with the following demonstrates the method.

let zebra = UIImage(named: "an_image_of_a_zebra")
print(zebra?.CGImage) // check the address
let shallowZebra = UIImage(CGImage: zebra!.CGImage!) 
print(shallowZebra.CGImage!) // same address

let zebraData = UIImagePNGRepresentation(zebra!)
let newZebra = UIImage(data: zebraData!)
print(newZebra?.CGImage) // new address