View Snapshots on iOS 7

Q:  On iOS 7 and later, how do I take a snapshot of my view and save the result in a UIImage?

A: Starting from iOS 7, the UIView class provides a method -drawViewHierarchyInRect:afterScreenUpdates:, which lets you render a snapshot of the complete view hierarchy as visible onscreen into a bitmap context. On iOS 6 and earlier, how to capture a view's drawing contents depends on the underlying drawing technique. This new method -drawViewHierarchyInRect:afterScreenUpdates: enables you to capture the contents of the receiver view and its subviews to an image regardless of the drawing techniques (for example UIKit, Quartz, OpenGL ES, SpriteKit, etc) in which the views are rendered.

See Listing 1 for an example of how to use -drawViewHierarchyInRect:afterScreenUpdates: to take a view snapshot on iOS 7 and later.

Listing 1  Creating a snapshot image

- (UIImage *)snapshot:(UIView *)view

{

    UIGraphicsBeginImageContextWithOptions(view.bounds.size, YES, 0);

    [view drawViewHierarchyInRect:view.bounds afterScreenUpdates:YES];

    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    return image;

}

In addition to -drawViewHierarchyInRect:afterScreenUpdates:, UIView now provides another two snapshot related methods, -snapshotViewAfterScreenUpdates: and -resizableSnapshotViewFromRect:afterScreenUpdates:withCapInsets:. UIScreen also has -snapshotViewAfterScreenUpdates:. Unlike UIView's -drawViewHierarchyInRect:afterScreenUpdates:, these methods return a UIView object. If you are looking for a new snapshot view, use one of these methods. It will be more efficient than calling -drawViewHierarchyInRect:afterScreenUpdates: to render the view contents into a bitmap image yourself. You can use the returned view as a visual stand-in for the current view/screen in your app. For example, you might use a snapshot view for animations where updating a large view hierarchy might be expensive.

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