Creating a blurring overlay view

2018-12-31 20:38发布

In the Music app of the new iOS, we can see an album cover behind a view that blurs it.

How can something like that be accomplished? I've read the documentation, but did not find anything there.

21条回答
只若初见
2楼-- · 2018-12-31 21:26

Simple answer is Add a subview and change it's alpha.

UIView *mainView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 200, 200)];
UIView *subView = [[UIView alloc] initWithFrame:popupView.frame];
UIColor * backImgColor = [UIColor colorWithPatternImage:[UIImage imageNamed:@"blue_Img.png"]];
subView.backgroundColor = backImgColor;
subView.alpha = 0.5;
[mainView addSubview:subView];
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低头抚发
3楼-- · 2018-12-31 21:28

Found this by accident, gives me really great (near duplicate with Apple's) results and uses the Acceleration framework. -- http://pastebin.com/6cs6hsyQ *Not written by me

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残风、尘缘若梦
4楼-- · 2018-12-31 21:28

Here's a fast implementation in Swift using CIGaussianBlur:

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;
}
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浮光初槿花落
5楼-- · 2018-12-31 21:31

enter image description here

From Xcode you can do it easily. Follow the steps from xcode. Drage visual effect view on your uiview or imageview.

Happy Coding :)

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几人难应
6楼-- · 2018-12-31 21:32

Swift 3 Version of Kev's answer to return blurred image -

func blurBgImage(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);

        if let result = filter?.value(forKey: kCIOutputImageKey) as? CIImage{

            let rect = CGRect(origin: CGPoint(x: radius * 2,y :radius * 2), size: CGSize(width: image.size.width - radius * 4, height: image.size.height - radius * 4))

            if let cgImage = context.createCGImage(result, from: rect){
                return UIImage(cgImage: cgImage);
                }
        }
        return nil;
    }
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不流泪的眼
7楼-- · 2018-12-31 21:32

Core Image

Since that image in the screenshot is static, you could use CIGaussianBlur from Core Image (requires iOS 6). Here is sample: https://github.com/evanwdavis/Fun-with-Masks/blob/master/Fun%20with%20Masks/EWDBlurExampleVC.m

Mind you, this is slower than the other options on this page.

#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;
}

Stack blur (Box + Gaussian)

  • StackBlur This implements a mix of Box and Gaussian blur. 7x faster than non accelerated gaussian, but not so ugly as box blur. See a demo in here (Java plugin version) or here (JavaScript version). This algorithm is used in KDE and Camera+ and others. It doesn't use the Accelerate Framework but it's fast.

Accelerate Framework

  • 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;
    }

Other stuff

Andy Matuschak said on Twitter: “you know, a lot of the places where it looks like we're doing it in real time, it's static with clever tricks.”

At doubleencore.com they say “we’ve found that a 10 pt blur radius plus a 10 pt increase in saturation best mimics iOS 7’s blur effect under most circumstances”.

A peek at the private headers of Apple's SBFProceduralWallpaperView.

Finally, this isn't a real blur, but remember you can set rasterizationScale to get a pixelated image: http://www.dimzzy.com/blog/2010/11/blur-effect-for-uiview/

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