Set “opacity” of a CGLayer before draw?

Question

I have UIView subclass - actually a puzzle piece - with 2 different CGLayer initialized at initWithFrame.

In drawRect I have to blend this two layer, and the uppermost should have variable alpha depending on game-logic.

What is the best (most performance optimized) way to do this? Is there any CGLayer, or CGContext function that sets some alpha before drawing?

Answer 1

Set the -opacity of the layer. Remember that the layer's -opaque setting must be NO. The default is NO, but it's commonly set to YES for performance reasons.

If you're already doing -drawInContext:, then you can experiment with CGContextSetAlpha(). Generally, though, you don't use -drawRect: and layers at the same time. You usually let either the view or the layers do the drawing.