renderInContext does not capture rotated subviews

core-animation, ios, objective-c, uikit

Solution

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];

Problem

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?

Original source