UIBackdropView

_UIBackdropView is a private class in UIKit.framework (iOS 7.0 +), which is used for the popular blur effects.

It uses a gaussianBlur CAFilter.

Here is a sample of _UIBackdropView

        Class UIBackDropView = objc_getClass("_UIBackdropView");
        if (UIBackDropView)
        {
            id settings = nil;
            
            Class _UIBackdropViewSettingsAdaptiveLight = objc_getClass("_UIBackdropViewSettingsAdaptiveLight");
            if (_UIBackdropViewSettingsAdaptiveLight)
            {
                settings = [_UIBackdropViewSettingsAdaptiveLight settingsForStyle:2060]; // 2060 is the system control center background view style
            }
            
            UIView * backView = (UIView *) [[UIBackDropView alloc] initWithFrame:CGRectMake(0, 0, 0, 0)
                                                         autosizesToFitSuperview:YES
                                                                        settings:settings];
            [self addSubview:backView];
            [backView release];
        }