Position a View for drawing via renderInContext:
calayer, cgcontext, core-graphics, ios
Solution
The geometry of the graphics context can be adjusted to the `UIView`s geometry with this snippet:
// Center the context around the view's anchor point
CGContextTranslateCTM(context, [view center].x, [view center].y);
// Apply the view's transform about the anchor point
CGContextConcatCTM(context, [view transform]);
// Offset by the portion of the bounds left of and above the anchor point
CGContextTranslateCTM(context,
-[view bounds].size.width * [[view layer] anchorPoint].x,
-[view bounds].size.height * [[view layer] anchorPoint].y);
Problem
I want to draw a `UIView` in my current `CGGraphicsContext`. I draw the `UIView` via `renderInContext:`, but it's not positioned correctly (always in the top left corner). I have all values of the `UIView` available for drawing the `UIView`. ``` CGRect frame; CGRect bound; CGPoint center; CGAffineTransform transform; ``` I currently set the position and rotation of the layer like this: ``` CGContextTranslateCTM(context, frame.origin.x, frame.origin.y); CGContextRotateCTM(context, (CGFloat) atan2(transform.b, transform.a)); ``` But the position is, due to the rotation, not correct and differs from the original position. How can I restore the original position? The coordinate system hasn't changed in between, it's just an issue to translate the `center.x` and `center.y` values into something appropriate for `CGContextTranslateCTM`. Edit: The saved values are correct, saving the correct `bounds`, `center` and `transform` is not the origin of my issue, the origin of my issue, is setting theses values to the drawable `CGLayer` via `CGContextTranslateCTM`.