UIKit. How to set Transparent color?

Question

Is there any way to set any color of UIImage (or it CALayer content) as transparent color?

I cannot use single image resource(PNG file) with built-in transparency.

I need to hide some area from first Layer by overlaying second Layer with specific color at that place. So I need to set this specific color as "transparent color" before assembled image drawing.

Image area I need to hide is like background - i.e. specific color will be started from image borders through whole perimeter.

EDIT: just found similar question here

Answer 1

Sounds like you need to use CGImageCreateWithMaskingColors. I recommend reading the "Bitmap Images and Image Masks" part of the Quartz Programming Guide, and check some example code. It's slightly more low-level than your average Cocoa code, but not very hard to accomplish.

Answer 2

I just updated a similar question with some more details here