CODEWITHSUNDEEP
ioscore-graphicscglayer
Terry
Terry

Reputation: 337

Duplicate sub-area within a CGLayer

I use Core Graphics to draw in an UIView, and cache the contents in a CGLayer.

One of its functions needs to duplicate a sub-area of the CGLayer and move it to a new location within the same layer. As a traditional trick, I used to do this by drawing the layer into its own context.

However, the behavior of this trick is "undefined" according to the documentation, and it stops working in iOS 12.

Is there an alternative way to do this efficiently? (I have tried drawing the sub-area into an CGImage then drawing the result image back to the layer. But this method seems sort of slow and not so memory efficient.:()

Upvotes: 1

Views: 41

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