I do not understand where the method mentioned in the title comes from, nor the other classes with the prefix 'CG', of core graphics. I searched for the framework 'Core Graphics' but it does not appear in UIKIT or in Cocoa touch.
One more thing, what would be a context? I read it in the api but I did not understand it.
CGGetCurrentContext is the call sign for the context in CoreGraphics.
let miContexto = UIGraphicsGetCurrentContext()
CGContextSaveGState(miContexto);
Context can be defined as a reference that the Operating System needs to know where information is being stored, for example, in which UIImageView you have an image stored.
This definition seems right to CG:
The context tells each CG call where to find all these "things" of his current "Drawing" call, gives a different context for it drawing call, and that call could draw a bitmap different in a completely different view, with one color different, different scale, etc.
definition taken from:
link (English)