下面是一个简单的方法来添加自定义模糊，而不用与私有api讨价还价使用UIViewPropertyAnimator:

首先，声明class属性:

var blurAnimator: UIViewPropertyAnimator!

然后在viewDidLoad()中设置你的模糊视图:

let blurEffectView = UIVisualEffectView()
blurEffectView.backgroundColor = .clear
blurEffectView.frame = view.bounds
blurEffectView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
view.addSubview(blurEffectView)

blurAnimator = UIViewPropertyAnimator(duration: 1, curve: .linear) { [blurEffectView] in
    blurEffectView.effect = UIBlurEffect(style: .light)
}

blurAnimator.fractionComplete = 0.15 // set the blur intensity.    

注意:此解决方案不适用于UICollectionView/UITableView单元格

核心形象

由于截图中的图像是静态的，你可以使用Core image中的CIGaussianBlur(需要iOS 6)。以下是示例:https://github.com/evanwdavis/Fun-with-Masks/blob/master/Fun%20with%20Masks/EWDBlurExampleVC.m

注意，这比本页上的其他选项要慢。

#import <QuartzCore/QuartzCore.h>

- (UIImage*) blur:(UIImage*)theImage
{   
    // ***********If you need re-orienting (e.g. trying to blur a photo taken from the device camera front facing camera in portrait mode)
    // theImage = [self reOrientIfNeeded:theImage];

    // create our blurred image
    CIContext *context = [CIContext contextWithOptions:nil];
    CIImage *inputImage = [CIImage imageWithCGImage:theImage.CGImage];

    // setting up Gaussian Blur (we could use one of many filters offered by Core Image)
    CIFilter *filter = [CIFilter filterWithName:@"CIGaussianBlur"];
    [filter setValue:inputImage forKey:kCIInputImageKey];
    [filter setValue:[NSNumber numberWithFloat:15.0f] forKey:@"inputRadius"];
    CIImage *result = [filter valueForKey:kCIOutputImageKey];

    // CIGaussianBlur has a tendency to shrink the image a little, 
    // this ensures it matches up exactly to the bounds of our original image
    CGImageRef cgImage = [context createCGImage:result fromRect:[inputImage extent]];

    UIImage *returnImage = [UIImage imageWithCGImage:cgImage];//create a UIImage for this function to "return" so that ARC can manage the memory of the blur... ARC can't manage CGImageRefs so we need to release it before this function "returns" and ends.
    CGImageRelease(cgImage);//release CGImageRef because ARC doesn't manage this on its own.

    return returnImage;

    // *************** if you need scaling
    // return [[self class] scaleIfNeeded:cgImage];
}

+(UIImage*) scaleIfNeeded:(CGImageRef)cgimg {
    bool isRetina = [[[UIDevice currentDevice] systemVersion] intValue] >= 4 && [[UIScreen mainScreen] scale] == 2.0;
    if (isRetina) {
        return [UIImage imageWithCGImage:cgimg scale:2.0 orientation:UIImageOrientationUp];
    } else {
        return [UIImage imageWithCGImage:cgimg];
    }
}

- (UIImage*) reOrientIfNeeded:(UIImage*)theImage{

    if (theImage.imageOrientation != UIImageOrientationUp) {

        CGAffineTransform reOrient = CGAffineTransformIdentity;
        switch (theImage.imageOrientation) {
            case UIImageOrientationDown:
            case UIImageOrientationDownMirrored:
                reOrient = CGAffineTransformTranslate(reOrient, theImage.size.width, theImage.size.height);
                reOrient = CGAffineTransformRotate(reOrient, M_PI);
                break;
            case UIImageOrientationLeft:
            case UIImageOrientationLeftMirrored:
                reOrient = CGAffineTransformTranslate(reOrient, theImage.size.width, 0);
                reOrient = CGAffineTransformRotate(reOrient, M_PI_2);
                break;
            case UIImageOrientationRight:
            case UIImageOrientationRightMirrored:
                reOrient = CGAffineTransformTranslate(reOrient, 0, theImage.size.height);
                reOrient = CGAffineTransformRotate(reOrient, -M_PI_2);
                break;
            case UIImageOrientationUp:
            case UIImageOrientationUpMirrored:
                break;
        }

        switch (theImage.imageOrientation) {
            case UIImageOrientationUpMirrored:
            case UIImageOrientationDownMirrored:
                reOrient = CGAffineTransformTranslate(reOrient, theImage.size.width, 0);
                reOrient = CGAffineTransformScale(reOrient, -1, 1);
                break;
            case UIImageOrientationLeftMirrored:
            case UIImageOrientationRightMirrored:
                reOrient = CGAffineTransformTranslate(reOrient, theImage.size.height, 0);
                reOrient = CGAffineTransformScale(reOrient, -1, 1);
                break;
            case UIImageOrientationUp:
            case UIImageOrientationDown:
            case UIImageOrientationLeft:
            case UIImageOrientationRight:
                break;
        }

        CGContextRef myContext = CGBitmapContextCreate(NULL, theImage.size.width, theImage.size.height, CGImageGetBitsPerComponent(theImage.CGImage), 0, CGImageGetColorSpace(theImage.CGImage), CGImageGetBitmapInfo(theImage.CGImage));

        CGContextConcatCTM(myContext, reOrient);

        switch (theImage.imageOrientation) {
            case UIImageOrientationLeft:
            case UIImageOrientationLeftMirrored:
            case UIImageOrientationRight:
            case UIImageOrientationRightMirrored:
                CGContextDrawImage(myContext, CGRectMake(0,0,theImage.size.height,theImage.size.width), theImage.CGImage);
                break;

            default:
                CGContextDrawImage(myContext, CGRectMake(0,0,theImage.size.width,theImage.size.height), theImage.CGImage);
                break;
        }

        CGImageRef CGImg = CGBitmapContextCreateImage(myContext);
        theImage = [UIImage imageWithCGImage:CGImg];

        CGImageRelease(CGImg);
        CGContextRelease(myContext);
    }

    return theImage;
}

叠加模糊(方块+高斯)

这实现了盒子和高斯模糊的混合。比非加速高斯快7倍，但不像盒子模糊那么难看。请在这里(Java插件版本)或这里(JavaScript版本)查看演示。该算法用于KDE和Camera+等。它不使用加速框架，但速度很快。

加速框架

In the session “Implementing Engaging UI on iOS” from WWDC 2013 Apple explains how to create a blurred background (at 14:30), and mentions a method applyLightEffect implemented in the sample code using Accelerate.framework. GPUImage uses OpenGL shaders to create dynamic blurs. It has several types of blur: GPUImageBoxBlurFilter, GPUImageFastBlurFilter, GaussianSelectiveBlur, GPUImageGaussianBlurFilter. There is even a GPUImageiOSBlurFilter that “should fully replicate the blur effect provided by iOS 7's control panel” (tweet, article). The article is detailed and informative.

    -(UIImage *)blurryGPUImage:(UIImage *)image withBlurLevel:(NSInteger)blur {
        GPUImageFastBlurFilter *blurFilter = [GPUImageFastBlurFilter new];
        blurFilter.blurSize = blur;
        UIImage *result = [blurFilter imageByFilteringImage:image];
        return result;
    }

From indieambitions.com: Perform a blur using vImage. The algorithm is also used in iOS-RealTimeBlur. From Nick Lockwood: https://github.com/nicklockwood/FXBlurView The example shows the blur over a scroll view. It blurs with dispatch_async, then syncs to call updates with UITrackingRunLoopMode so the blur is not lagged when UIKit gives more priority to the scroll of the UIScrollView. This is explained in Nick's book iOS Core Animation, which btw it's great. iOS-blur This takes the blurring layer of the UIToolbar and puts it elsewhere. Apple will reject your app if you use this method. See https://github.com/mochidev/MDBlurView/issues/4 From Evadne blog: LiveFrost: Fast, Synchronous UIView Snapshot Convolving. Great code and a great read. Some ideas from this post: Use a serial queue to throttle updates from CADisplayLink. Reuse bitmap contexts unless bounds change. Draw smaller images using -[CALayer renderInContext:] with a 0.5f scale factor.

其他东西

安迪·马图斯查克在推特上说:“你知道，在很多地方，我们看起来是实时的，但它是静态的，用的是聪明的技巧。”

在doubleencore.com网站上，他们说:“我们发现，在大多数情况下，10点模糊半径加上10点饱和度的增加最能模拟iOS 7的模糊效果。”

苹果sbfproceuralwallpaperview的私有头文件。

最后，这不是一个真正的模糊，但记住你可以设置rasterizationScale来获得一个像素化的图像:http://www.dimzzy.com/blog/2010/11/blur-effect-for-uiview/

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。

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;
}

我不认为我被允许发布代码，但上面提到的WWDC示例代码是正确的。链接如下:https://developer.apple.com/downloads/index.action?name=WWDC%202013

你要找的文件是UIImage上的category，方法是applyLightEffect。

正如我在上面的评论中提到的，除了模糊，苹果模糊还有饱和度和其他东西。简单的模糊是不行的……如果你想模仿他们的风格。

公认的答案是正确的，但这里缺少一个重要的步骤，如果这个视图-您想要模糊的背景-是使用

[self presentViewController:vc animated:YES completion:nil]

默认情况下，这将抵消模糊，因为UIKit删除演示者的视图，这实际上是模糊的。为了避免这种删除，将这一行添加到前一行之前

vc。modalPresentationStyle = UIModalPresentationOverFullScreen;

或者使用其他Over样式。