How can I multiply an image against the alpha of another image in Cocoa?

Question

Having loaded two different images I want to do the following operation and obtain image3.

image1.red * image2.alpha = image3.red
image1.green * image2.alpha = image3.green
image1.blue * image2.alpha = image3.blue

I wrote the code in the link below for Android and was basically looking for the same functionality in Objective-C/Cocoa.
http://www.ruibm.com/?p=184

Thanks, Rui

Answer 1

Draw a rounded rectangle path and clip your image with it.

http://developer.apple.com/mac/library/documentation/GraphicsImaging/Conceptual/drawingwithquartz2d/dq%5Fimages/dq%5Fimages.html#//apple%5Fref/doc/uid/TP30001066-CH212-CJBHBCGB