objective - c

UIVisualEffect *blurEffect;
blurEffect = [UIBlurEffect effectWithStyle:UIBlurEffectStyleDark];
UIVisualEffectView *visualEffectView;
visualEffectView = [[UIVisualEffectView alloc] initWithEffect:blurEffect];
visualEffectView.frame = self.accessImageView.bounds;
[self.accessImageView addSubview:visualEffectView];

斯威夫特3.0

let blurEffect = UIBlurEffect(style: UIBlurEffectStyle.dark)
let blurEffectView = UIVisualEffectView(effect: blurEffect)
blurEffectView.frame = view.bounds
blurEffectView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
view.addSubview(blurEffectView)

来源:https://stackoverflow.com/a/24083728/4020910

下面是Swift中使用CIGaussianBlur的快速实现:

func blur(image image: UIImage) -> UIImage {
    let radius: CGFloat = 20;
    let context = CIContext(options: nil);
    let inputImage = CIImage(CGImage: image.CGImage!);
    let filter = CIFilter(name: "CIGaussianBlur");
    filter?.setValue(inputImage, forKey: kCIInputImageKey);
    filter?.setValue("\(radius)", forKey:kCIInputRadiusKey);
    let result = filter?.valueForKey(kCIOutputImageKey) as! CIImage;
    let rect = CGRectMake(radius * 2, radius * 2, image.size.width - radius * 4, image.size.height - radius * 4)
    let cgImage = context.createCGImage(result, fromRect: rect);
    let returnImage = UIImage(CGImage: cgImage);

    return returnImage;
}

2019代码

下面是一个使用@AdamBardon技巧的更完整的例子。

@IBDesignable class ButtonOrSomethingWithBlur: UIButton {

    var ba: UIViewPropertyAnimator?
    private lazy var blurry: BlurryBall = { return BlurryBall() }()

    override func didMoveToSuperview() {
        super.didMoveToSuperview()
        
        // Setup the blurry ball.  BE SURE TO TEARDOWN.
        // Use superb trick to access the internal guassian level of Apple's
        // standard gpu blurrer per stackoverflow.com/a/55378168/294884
        
        superview?.insertSubview(blurry, belowSubview: self)
        ba = UIViewPropertyAnimator(duration:1, curve:.linear) {[weak self] in
            // note, those duration/curve values are simply unusued
            self?.blurry.effect = UIBlurEffect(style: .extraLight)
        }
        ba?.fractionComplete = live.largeplaybutton_blurfactor
    }
    
    override func willMove(toSuperview newSuperview: UIView?) {
        
        // Teardown for the blurry ball - critical
        
        if newSuperview == nil { print("safe teardown")
            ba?.stopAnimation(true)
            ba?.finishAnimation(at: .current)
        }
    }

    override func layoutSubviews() { super.layoutSubviews()
        blurry.frame = bounds, your drawing frame or whatever
    }

{题外话:作为一个通用的iOS工程问题，didMoveToWindow可能比didMoveToSuperview更适合你。其次，您可以使用其他一些方法来执行拆卸操作，但是拆卸操作就是这里显示的两行代码。

bluryball只是一个UIVisualEffectView。注意视觉效果视图的初始值。如果你碰巧需要圆角或者其他东西，在这门课上做吧。

class BlurryBall: UIVisualEffectView {
    
    override init(effect: UIVisualEffect?) { super.init(effect: effect)
        commonInit() }
    
    required init?(coder aDecoder: NSCoder) { super.init(coder: aDecoder)
        commonInit() }
    
    private func commonInit() {
        clipsToBounds = true
        backgroundColor = .clear
    }
    
    override func layoutSubviews() {
        super.layoutSubviews()
        layer.cornerRadius = bounds.width / 2
    }
}

这个答案是基于Mitja Semolic之前出色的回答。我已经将它转换为swift 3，添加了一个解释，在评论中发生了什么，使它成为一个UIViewController的扩展，这样任何VC都可以随意调用它，添加了一个未模糊的视图来显示选择性应用，并添加了一个完成块，以便调用视图控制器可以在完成模糊时做任何它想做的事情。

    import UIKit
//This extension implements a blur to the entire screen, puts up a HUD and then waits and dismisses the view.
    extension UIViewController {
        func blurAndShowHUD(duration: Double, message: String, completion: @escaping () -> Void) { //with completion block
            //1. Create the blur effect & the view it will occupy
            let blurEffect = UIBlurEffect(style: UIBlurEffectStyle.light)
            let blurEffectView = UIVisualEffectView()//(effect: blurEffect)
            blurEffectView.frame = self.view.bounds
            blurEffectView.autoresizingMask = [.flexibleWidth, .flexibleHeight]

        //2. Add the effect view to the main view
            self.view.addSubview(blurEffectView)
        //3. Create the hud and add it to the main view
        let hud = HudView.getHUD(view: self.view, withMessage: message)
        self.view.addSubview(hud)
        //4. Begin applying the blur effect to the effect view
        UIView.animate(withDuration: 0.01, animations: {
            blurEffectView.effect = blurEffect
        })
        //5. Halt the blur effects application to achieve the desired blur radius
        self.view.pauseAnimationsInThisView(delay: 0.004)
        //6. Remove the view (& the HUD) after the completion of the duration
        DispatchQueue.main.asyncAfter(deadline: .now() + duration) {
            blurEffectView.removeFromSuperview()
            hud.removeFromSuperview()
            self.view.resumeAnimationsInThisView()
            completion()
        }
    }
}

extension UIView {
    public func pauseAnimationsInThisView(delay: Double) {
        let time = delay + CFAbsoluteTimeGetCurrent()
        let timer = CFRunLoopTimerCreateWithHandler(kCFAllocatorDefault, time, 0, 0, 0, { timer in
            let layer = self.layer
            let pausedTime = layer.convertTime(CACurrentMediaTime(), from: nil)
            layer.speed = 0.0
            layer.timeOffset = pausedTime
        })
        CFRunLoopAddTimer(CFRunLoopGetCurrent(), timer, CFRunLoopMode.commonModes)
    }
    public func resumeAnimationsInThisView() {
        let pausedTime  = layer.timeOffset

        layer.speed = 1.0
        layer.timeOffset = 0.0
        layer.beginTime = layer.convertTime(CACurrentMediaTime(), from: nil) - pausedTime
    }
}

我已经确认它适用于iOS 10.3.1和iOS 11

我决定发布一个书面的Objective-C版本，从接受的答案只是在这个问题上提供更多的选项。

- (UIView *)applyBlurToView:(UIView *)view withEffectStyle:(UIBlurEffectStyle)style andConstraints:(BOOL)addConstraints
{
  //only apply the blur if the user hasn't disabled transparency effects
  if(!UIAccessibilityIsReduceTransparencyEnabled())
  {
    UIBlurEffect *blurEffect = [UIBlurEffect effectWithStyle:style];
    UIVisualEffectView *blurEffectView = [[UIVisualEffectView alloc] initWithEffect:blurEffect];
    blurEffectView.frame = view.bounds;

    [view addSubview:blurEffectView];

    if(addConstraints)
    {
      //add auto layout constraints so that the blur fills the screen upon rotating device
      [blurEffectView setTranslatesAutoresizingMaskIntoConstraints:NO];

      [view addConstraint:[NSLayoutConstraint constraintWithItem:blurEffectView
                                                       attribute:NSLayoutAttributeTop
                                                       relatedBy:NSLayoutRelationEqual
                                                          toItem:view
                                                       attribute:NSLayoutAttributeTop
                                                      multiplier:1
                                                        constant:0]];

      [view addConstraint:[NSLayoutConstraint constraintWithItem:blurEffectView
                                                       attribute:NSLayoutAttributeBottom
                                                       relatedBy:NSLayoutRelationEqual
                                                          toItem:view
                                                       attribute:NSLayoutAttributeBottom
                                                      multiplier:1
                                                        constant:0]];

      [view addConstraint:[NSLayoutConstraint constraintWithItem:blurEffectView
                                                       attribute:NSLayoutAttributeLeading
                                                       relatedBy:NSLayoutRelationEqual
                                                          toItem:view
                                                       attribute:NSLayoutAttributeLeading
                                                      multiplier:1
                                                        constant:0]];

      [view addConstraint:[NSLayoutConstraint constraintWithItem:blurEffectView
                                                       attribute:NSLayoutAttributeTrailing
                                                       relatedBy:NSLayoutRelationEqual
                                                          toItem:view
                                                       attribute:NSLayoutAttributeTrailing
                                                      multiplier:1
                                                        constant:0]];
    }
  }
  else
  {
    view.backgroundColor = [[UIColor blackColor] colorWithAlphaComponent:0.7];
  }

  return view;
}

如果你想要，如果你只支持纵向模式，或者我只是在这个函数中添加了一个标志来使用它们，可以删除这些限制。

自定义模糊比例

你可以尝试UIVisualEffectView自定义设置为-

class BlurViewController: UIViewController {
    private let blurEffect = (NSClassFromString("_UICustomBlurEffect") as! UIBlurEffect.Type).init()

    override func viewDidLoad() {
        super.viewDidLoad()
        let blurView = UIVisualEffectView(frame: UIScreen.main.bounds)
        blurEffect.setValue(1, forKeyPath: "blurRadius")
        blurView.effect = blurEffect
        view.addSubview(blurView)
    }   
}

输出:- for blureeffect . setvalue(1…& blurEffect.setValue (2 . .