renderInContext does not capture rotated subviews

Question

A UIImageVIew (imageView) is added to self.view, capturing the view to album works perfectly:

 CGSize size = CGSizeMake(self.view.frame.size.height, self.view.frame.size.width);
 UIGraphicsBeginImageContext(size);
 [self.view.layer renderInContext:UIGraphicsGetCurrentContext()];
 UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
 UIGraphicsEndImageContext();
 UIImageWriteToSavedPhotosAlbum(image, self, nil, nil);

However, if the imageView subview is rotated by:

 [CABasicAnimation animationWithKeyPath:@"transform.rotation.z"];

Capturing self.view again does not reflected the rotation. The subview imageView is as if not rotated.

How to make renderInContext works with subviews rotated by CABasicAnimation?

UPDATE:

Warning: The CALayer/-renderInContext: method doesn't implement the full Core Animation composition model. The code provided below will be able to resolve most of the situations, but there are things that the CALayer/-renderInContext: method doesn't render correctly, so you may wish to contact Developer Technical Support for workaround requests.

Official Apple Technical Q&A QA1703 suggested to contact Developer Technical Support for workaround requests.

Is there a workaround already existed?

Answer 1

Use layer.presentationLayer instead of layer when renderInContext.

Here is a category for taking screenshots of UIView, UIView+Screenshot.h:

 //
 //  UIView+Screenshot.h
 //
 //  Created by Horace Ho on 2012/12/11.
 //  Copyright (c) 2012 Horace Ho. All rights reserved.
 //
 // Permission is hereby granted, free of charge, to any person obtaining a copy
 // of this software and associated documentation files (the "Software"), to deal
 // in the Software without restriction, including without limitation the rights
 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 // copies of the Software, and to permit persons to whom the Software is
 // furnished to do so, subject to the following conditions:
 //
 // The above copyright notice and this permission notice shall be included in
 // all copies or substantial portions of the Software.
 //
 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 // THE SOFTWARE.

 @interface UIView (HHScreenShot)
 - (UIImage *)screenshot:(UIDeviceOrientation)orientation isOpaque:(BOOL)isOpaque usePresentationLayer:(BOOL)usePresentationLayer;
 @end

 @implementation UIView (HHScreenShot)

 - (UIImage *)screenshot:(UIDeviceOrientation)orientation isOpaque:(BOOL)isOpaque usePresentationLayer:(BOOL)usePresentationLayer
 {
     CGSize size;

     if (orientation == UIDeviceOrientationPortrait || orientation == UIDeviceOrientationPortraitUpsideDown) {
         size = CGSizeMake(self.frame.size.width, self.frame.size.height);
     } else {
         size = CGSizeMake(self.frame.size.height, self.frame.size.width);
     }

     UIGraphicsBeginImageContextWithOptions(size, isOpaque, 0.0);

     if (usePresentationLayer) {
         [self.layer.presentationLayer renderInContext:UIGraphicsGetCurrentContext()];
     } else {
         [self.layer renderInContext:UIGraphicsGetCurrentContext()];
     }

     UIImage *image = UIGraphicsGetImageFromCurrentImageContext();

     UIGraphicsEndImageContext();

     return image;
 }

 @end

To use:

 UIImage *image = [self.view screenshot:UIDeviceOrientationPortrait
                               isOpaque:YES 
                   usePresentationLayer:YES];

Answer 2

From the documentation:

This method renders directly from the layer tree, ignoring any animations added to the render tree.

You would have to read the rotation from the presentation layer and rotate the graphics context.