Draw an image in Additive Blend Mode without using OpenGL

I want to draw an image using an additive blend mode. But I don't want to use OpenGL. I can't find anything to do this, maybe there's something in Quartz2D?

Can anyone point me in the开发者_如何学编程 right direction?

Cheers, Rich

Sure there is enum CGBlendMode which you can use to specify blending operation. use method:

CGContextSetBlendMode()

or

[image drawInRect:CGRectMake(0, 0, width, height) blendMode:mode alpha:1];

more at developer site: link text