title: Applying color to gray scale image, preserving alpha values (iOS/Quartz)
body: <p>This is probably very straightforward, but I am not even sure what it's called - which makes googling a bit less useful than usual.</p>
  
  <p>I have a gray scale line drawing with alpha for anti-aliasing effect. This drawing is used as a player token in a game. Currently, I have created a couple of colorized variants (in Photoshop). But I would like to be able to programmatically tint the original image, while preserving the alpha values. I am using Quartz/Core Graphics, and I suspect that there may be some sort of blend that would accomplish the desired effect - but not sure which or even if that's the right approach.</p>