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I just need to know hot to create a CGLayer that has an image drawn to it. I am not completely understanding the documentation entirely. Thanks

Jab
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  • For basic info on CGlayer, this may well help ... http://stackoverflow.com/questions/4458812/whats-the-difference-and-compatibility-of-cglayer-and-calayer/4594394#4594394 – Fattie Apr 17 '12 at 14:09

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A while ago I posted a blog post on a similar topic, available here:

Drawing UIImages right side up using CoreGraphics

In that post, I show how to draw a UIImage so that's it's grayscale. Part of that includes creating a new layer with a gray colorspace (so it draws in shades of gray), and then extracting the CGContextRef from the CGLayer, pushing it to the context stack, drawing the UIImage, and then popping the context stack. The UIImage draws onto the topmost CGContextRef, which will be the context that corresponds to your CGLayer.

There are probably other ways to do this, but this is how I've done it in the past, and it's always worked great for me.

Dave DeLong
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  • When changing the .image property of an UIImageView, do you know if the system is using CGLayer to get good performance ? Or do I need to use your code to get a better FPS ? – CedricSoubrie Aug 22 '11 at 09:26
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    @Cedric it's getting passed through to the underlying `CALayer`, so it's not going through a `CGLayer` at all. – Dave DeLong Aug 22 '11 at 13:27