UIColor and CIColor how do they compare and what is the purpose of having two of them?

Question

Recently I encountered some code where trying to get the CIColor property of a UIColor fails. The UIColor was initialized as a simple [UIColor blackColor] and trying to get the

Answer 1

The documentation for the CIColor property on UIImage says:

This property throws an exception if the color object was not initialized with a Core Image color.

So if you want to access a UIColor's CIColor, it needs to have been created from a CIColor in the first place.

On the other hand, you can make a new CIColor from any UIColor using the initWithColor: initializer:

CIColor *color = [[CIColor alloc] initWithColor:UIColor.blackColor];