CALayer's backgroundFilters doesn nothing on UIView
calayer, ios, ios6
Solution
The reason for CALayer's backgroundFilters doing nothing on UIView is that unfortunately the `backgroundFilters` property is not supported on layers in iOS. It's inside inside the documentation, at the very end of the description:
Special Considerations
This property is not supported on layers in iOS.
I got bitten by this myself trying to insert a `UIView` that blurs the contents behind it. To blur a view on iOS, some more work seems to be required (copying the UIViews content inside an image, then blurring and showing the image).
Problem
I am trying to add a CIFilter to the backgroundFilters property of a `CALayer` to let this draw in a `UIView`. Therefore I subclassed `CALayer` and in the init execute the following: ``` CIFilter* blur = [CIFilter filterWithName:@"CIGaussianBlur"]; [blur setDefaults]; [blur setValue:@(10) forKey:@"inputRadius"]; self.backgroundFilters = @[ blur ]; ``` Then I created a subclass of `UIView` that has this custom Layer as it's layer by returning the layers class in `+[UIView layerClass]` This is working, the above code is executed! However if I place this view above a `UIImageView` I would expect the image to be drawn blured where I put this view. But it doesn't! The view just behaves like a regular view and takes any color / alpha value I set to it's `backgroundColor` property, but I just see the underlaying `UIImageView` as it is, without a blur!