Purpose

FXBlurView is a UIView subclass that replicates the iOS 7 realtime background blur effect, but works on iOS 5 and above. It is designed to be as fast and as simple to use as possible. FXBlurView offers two modes of operation: static, where the view is rendered only once when it is added to a superview (though it can be updated by calling setNeedsDisplay or updateAsynchronously:completion:) or dynamic, where it will automatically redraw itself on a background thread as often as possible.

Supported iOS & SDK Versions

• Supported build target - iOS 8.4 (Xcode 6.4, Apple LLVM compiler 6.1)
• Earliest supported deployment target - iOS 7.0
• Earliest compatible deployment target - iOS 4.3

NOTE: 'Supported' means that the library has been tested with this version. 'Compatible' means that the library should work on this iOS version (i.e. it doesn't rely on any unavailable SDK features) but is no longer being tested for compatibility and may require tweaking or bug fixes to run correctly.

ARC Compatibility

As of version 1.3, FXBlurView requires ARC. If you wish to use FXBlurView in a non-ARC project, just add the -fobjc-arc compiler flag to the FXBlurView.m class. To do this, go to the Build Phases tab in your target settings, open the Compile Sources group, double-click FXBlurView.m in the list and type -fobjc-arc into the popover.

If you wish to convert your whole project to ARC, comment out the #error line in FXBlurView.m, then run the Edit > Refactor > Convert to Objective-C ARC... tool in Xcode and make sure all files that you wish to use ARC for (including FXBlurView.m) are checked.

Installation

To use FXBlurView, just drag the class files into your project and add the Accelerate framework. You can create FXBlurView instances programatically, or create them in Interface Builder by dragging an ordinary UIView into your view and setting its class to FXBlurView.

If you are using Interface Builder, to set the custom properties of FXBlurView (ones that are not supported by regular UIViews) either create an IBOutlet for your view and set the properties in code, or use the User Defined Runtime Attributes feature in Interface Builder (introduced in Xcode 4.2 for iOS 5+).

UIImage extensions

FXBlurView extends UIImage with the following method:

- (UIImage *)blurredImageWithRadius:(CGFloat)radius
                         iterations:(NSUInteger)iterations
                          tintColor:(UIColor *)tintColor;

This method applies a blur effect and returns the resultant blurred image without modifying the original. The radius property controls the extent of the blur effect. The iterations property controls the number of iterations. More iterations means higher quality. The tintColor is an optional color that will be blended with the resultant image. Note that the alpha component of the tintColor is ignored.

FXBlurView methods

+ (void)setBlurEnabled:(BOOL)blurEnabled;

This method can be used to globally enable/disable the blur effect on all FXBlurView instances. This is useful for testing, or if you wish to disable blurring on iPhone 4 and below (for consistency with iOS7 blur view behavior). By default blurring is enabled.

+ (void)setUpdatesEnabled;
+ (void)setUpdatesDisabled;

These methods can be used to enable and disable updates for all dynamic FXBlurView instances with a single command. Useful for disabling updates immediately before performing an animation so that the FXBlurView updates don't cause the animation to stutter. Calls can be nested, but ensure that the enabled/disabled calls are balanced, or the updates will be left permanently enabled or disabled.

- (void)updateAsynchronously:(BOOL)async completion:(void (^)())completion;

This method can be used to trigger an update of the blur effect (useful when dynamic = NO). The async argument controls whether the blur will be redrawn on the main thread or in the background. The completion argument is an optional callback block that will be called when the blur is completed.

- (void)setNeedsDisplay;

Inherited from UIView, this method can be used to trigger a (synchronous) update of the view. Calling this method is more-or-less equivalent to calling [view updateAsynchronously:NO completion:NULL].

FXBlurView properties

@property (nonatomic, getter = isBlurEnabled) BOOL blurEnabled;

This property toggles blurring on and off for an individual FXBlurView instance. Blurring is enabled by default. Note that if you disable blurring using the +setBlurEnabled method then that will override this setting.

@property (nonatomic, getter = isDynamic) BOOL dynamic;

This property controls whether the FXBlurView updates dynamically, or only once when the view is added to its superview. Defaults to YES. Note that if dynamic is set to NO, you can still force the view to update by calling setNeedsDisplay or updateAsynchronously:completion:. Dynamic blurring is extremely cpu-intensive, so you should always disable dynamic views immediately prior to performing an animation to avoid stuttering. However, if you have multiple FXBlurViews on screen then it is simpler to disable updates using the setUpdatesDisabled method rather than setting the dynamic property to NO.

@property (nonatomic, assign) NSUInteger iterations;

The number of blur iterations. More iterations improves the quality but reduces the performance. Defaults to 2 iterations.

@property (nonatomic, assign) NSTimeInterval updateInterval;

This controls the interval (in seconds) between successive updates when the FXBlurView is operating in dynamic mode. This defaults to zero, which means that the FXBlurView will update as fast as possible. This yields the best frame rate, but is also extremely CPU intensive and may cause the rest of your app's performance to degrade, especially on older devices. To alleviate this, try increasing the updateInterval value.

@property (nonatomic, assign) CGFloat blurRadius;   

This property controls the radius of the blur effect (in points). Defaults to a 40 point radius, which is similar to the iOS 7 blur effect.

@property (nonatomic, strong) UIColor *tintColor;

This in an optional tint color to be applied to the FXBlurView. The RGB components of the color will be blended with the blurred image, resulting in a gentle tint. To vary the intensity of the tint effect, use brighter or darker colors. The alpha component of the tintColor is ignored. If you do not wish to apply a tint, set this value to nil or [UIColor clearColor]. Note that if you are using Xcode 5 or above, FXBlurViews created in Interface Builder will have a blue tint by default.

@property (nonatomic, weak) UIView *underlyingView;

This property specifies the view that the FXBlurView will sample to create the blur effect. If set to nil (the default), this will be the superview of the blur view itself, but you can override this if you need to.

FAQ

Q. Why are my views all blue-tinted on iOS 7?
A. FXBlurView uses the `UIView` `tintColor` property, which does not exist on iOS 6 and below, but defaults to blue on iOS 7. Just set this property to `[UIColor clearColor]` to disable the tint. To retain iOS 6 compatibility, you can either set this using code, or by using the User Defined Runtime Attributes feature of Interface Builder, which will override the standard `tintColor` value (see the example project nibs for how to do this).

Q. FXBlurView makes my whole app run slowly on [old device], what can I do?
A. To improve performance, try increasing the `updatePeriod` property, reducing the `iterations` property or disabling `dynamic` unless you really need it. If all else fails, set `blurEnabled` to NO on older devices.

Q. My SpriteKit/OpenGL/Video/3D transformed content isn't showing up properly when placed underneath an FXBlurView, why not?
A. This is a limitation of a the `CALayer` `renderInContext:` method used to capture the view contents. There is no workaround for this on iOS 6 and earlier. On iOS 7 you can make use of the `UIView` `drawViewHierarchyInRect:afterScreenUpdates:` method to capture an view and apply the blur effect yourself, but this it too slow for realtime use, so FXBlurView does not use this method by default.

Q. FXBlurView is not capturing some ordinary view content that is behind it, why not?
A. FXBlurView captures the contents of its immediate superview by default. If the superview is transparent or partially transparent, content shown behind it will not be captured. You can override the `underlyingView` property to capture the contents of a different view if you need to.

Release Notes

Version 1.6.4

• blurredImageWithRadius:iterations:tintColor: now works if image is not in ARGB format
• Fixed ": CGContextRestoreGState: invalid context 0x0."
• Empty sublayers are now hidden before snapshotting to prevent renderInContext crash on iOS 8
• FXBlurView now automatically uses slower drawViewHierarchyInRect method when needed to capture content
• Added Travis integration

Version 1.6.3

• FXBlurView image background is no longer opaque/black, so it can be used as a translucent overlay
• underlyingView property is now an IBOutlet, so it can be connected in Interface Builder
• Moved imports into header for better Swift compatibility

Version 1.6.2

• Fixed crash on iOS 8 when animating blur
• Fixed issue when using FXBlurView with Swift

Version 1.6.1

• Fixed issue with animation completion block not firing

Version 1.6

• It is now possible to animate blurRadius
• Now requires QuartzCore framework

Version 1.5.6

• Fixed bug introduced in 1.5.4 where snapshot would always be taken from top-left corner of superview

Version 1.5.5

• Fixed zero-sized context warning in console when view has no presentationLayer

Version 1.5.4

• It is now possible to animate the FXBlurView frame using ordinary UIView animations

Version 1.5.3

• Fixed pixelation issue on non-Retina devices running iOS 6 or earlier

Version 1.5.2

• Fixed bug where edge of blur could be cropped short when using content modes other than scale to fit

Version 1.5.1

• Fixed bug where completion handler was not called for synchronous blur.

Version 1.5

• Added underlyingView property to specify source view
• Added updateAsynchronously:completion: method
• Fixed glitch with edges on certain views
• Now conforms to -Weverything warning level

Version 1.4.4

• Fixed pixelation issue on Retina iPads

Version 1.4.3

• Fixed error when compiling for iOS 6.1 SDK using Xcode 5

Version 1.4.2

• Fixed issue where shadow or ghosting could appear at edge of blur view
• Now conforms to -Wextra warning level

Version 1.4.1

• Fixed minor memory leak in the setUp method

Version 1.4

• More intelligent scheduling when multiple dynamic FXBlurView instances are shown on screen at once
• Added global and individual methods for disabling blur (e.g. so you can disable blur on iPhone 4 and below for consistency with other apps on iOS 7)
• Added Multiples views example

Version 1.3.3

• Fixed console warning when adding an FXBlurView of zero size to the window

Version 1.3.2

• Fixed issue with pixelation on non-Retina devices
• Tweaked performance/quality tradeoff

Version 1.3.1

• Improved blur quality (1.3 was slightly blocky)

Version 1.3

• Added tintColor property
• Significant performance improvement by reducing snapshot scale based in proportion to blur radius
• Views placed in front of the FXBlurView in the hierarchy are no longer included in the blur effect
• Fixed issue where blurView was sometimes partially transparent
• Added example showing how to implement an iOS7 control center-style overlay
• FXBlurView now requires ARC

Version 1.2

• Added +setUpdatesEnabled and +setUpdatesDisabled methods to globally enable/disable dynamic blur updates (e.g. when performing an animation)
• Added -updateInterval method to control CPU load when updating
• Changed runloop mode to reduce interference with scrolling, etc

Version 1.1

• Added ability to set number of blur iterations
• Fixed setNeedsDisplay behavior when dynamic = NO
• Reduced memory allocations in blur algorithm
• Added dynamic mode toggle to example app

Version 1.0

• Initial release