How to create a UIImage from whatever is in the background

Question

I am applying blur to various sections of my app using the UIImage+ImageEffects.h sample code that was provided in one of the apps from the WWDC in 2013. It works well and I'm able to recreate the iOS7 effects for any UIImage.

However, I would like to recreate the effect of the UINavigationBar blurred transparency but using any view that I choose. Similar to the screenshot shown below.

For instance, say that I have a UITableView that takes up half of the screen. I also have a UIImageView background as a separate view behind it that occupies the entire screen. I would only like to blur the UIImageView background for just that section of the screen that's under the tableview.

Here's my question. How do I create create a UIImage by taking a "screenshot" of whatever is behind a UIView that is displayed? Is this even possible?

Thanks!

Here is my screen hierarchy. Nothing complex. I would like the "Blurred Image View" to contain a blurred image of the section of the "Image View" that is sitting as the main UIImageView in the hierarchy.

Answer 1

If you are deploing only on iOS7 you can use the new api, that are a lot faster than -renderInContext and use the ImageEffects category on that image taken from the view. Add this aa category on UIView

@interface UIView (RenderView)

- (UIImage *) imageByRenderingView;
- (UIImage *) imageByRenderingViewOpaque:(BOOL) yesOrNO;


@end

@implementation UIView (RenderView)

- (UIImage *) imageByRenderingViewOpaque:(BOOL) yesOrNO {
        UIGraphicsBeginImageContextWithOptions(self.bounds.size, yesOrNO, 0);

    if ([self respondsToSelector:@selector(drawViewHierarchyInRect:afterScreenUpdates:)]) {
        [self drawViewHierarchyInRect:self.bounds afterScreenUpdates:NO];
    }
    else {
        [self.layer renderInContext:UIGraphicsGetCurrentContext()];
    }
    UIImage *resultingImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return resultingImage;
}
- (UIImage *) imageByRenderingView{
    return [self imageByRenderingViewOpaque:NO];
}

This snippet is a UIView category ok also for system lower than iOS7. It takes an image on a view and its subviews.

Answer 2

Use the below piece of code for iOS < 7

#import <QuartzCore/QuartzCore.h>

+ (UIImage *) imageWithView:(UIView *)view
{
    UIGraphicsBeginImageContextWithOptions(view.bounds.size, view.opaque, 0.0);
    [view.layer renderInContext:UIGraphicsGetCurrentContext()];

    UIImage * img = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    return img;
}