@interface AppDelegate ()@property (nonatomic, weak)UIImageView *cover;@end

- (void)applicationDidEnterBackground:(UIApplication *)application {        UIImageView *imgView = [[UIImageView alloc] initWithFrame:[UIApplication sharedApplication].keyWindow.bounds];    self.cover = imgView;    [[UIApplication sharedApplication].keyWindow addSubview:imgView];    UIGraphicsBeginImageContext([UIApplication sharedApplication].keyWindow.size);    // 将当前layer的截图写进上下中    [[UIApplication sharedApplication].keyWindow.layer renderInContext:UIGraphicsGetCurrentContext()];    // 从上下中读取图片    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();　　// 压缩图片,并转成JPEG类型    NSData *imageData = http://www.mamicode.com/UIImageJPEGRepresentation(image, 0.01);    image = [UIImage imageWithData:imageData];　　// 注意：不能直接将图片毛玻璃化，要转成data后，再转成image，此时的image才能毛玻璃化，不然调用blurryImage:withBlurLevel会报错。    imgView.image = [UIImage blurryImage:image withBlurLevel:0.15];}- (void)applicationDidBecomeActive:(UIApplication *)application {        [self.cover removeFromSuperview];}

//加模糊效果，image是图片，blur是模糊度+ (UIImage *)blurryImage:(UIImage *)image withBlurLevel:(CGFloat)blur {    //模糊度,    if ((blur < 0.1f) || (blur > 2.0f)) {        blur = 0.5f;    }        //boxSize必须大于0    int boxSize = (int)(blur * 100);    boxSize -= (boxSize % 2) + 1;    NSLog(@"boxSize:%i",boxSize);    //图像处理    CGImageRef img = image.CGImage;    //需要引入#import <Accelerate/Accelerate.h>    /*     This document describes the Accelerate Framework, which contains C APIs for vector and matrix math, digital signal processing, large number handling, and image processing.     本文档介绍了Accelerate Framework，其中包含C语言应用程序接口（API）的向量和矩阵数学，数字信号处理，大量处理和图像处理。     */        //图像缓存,输入缓存，输出缓存    vImage_Buffer inBuffer, outBuffer;    vImage_Error error;    //像素缓存    void *pixelBuffer;        //数据源提供者，Defines an opaque type that supplies Quartz with data.    CGDataProviderRef inProvider = CGImageGetDataProvider(img);    // provider’s data.    CFDataRef inBitmapData =http://www.mamicode.com/ CGDataProviderCopyData(inProvider);        //宽，高，字节/行，data    inBuffer.width = CGImageGetWidth(img);    inBuffer.height = CGImageGetHeight(img);    inBuffer.rowBytes = CGImageGetBytesPerRow(img);    inBuffer.data = (void*)CFDataGetBytePtr(inBitmapData);        //像数缓存，字节行*图片高    pixelBuffer = malloc(CGImageGetBytesPerRow(img) * CGImageGetHeight(img));        outBuffer.data = pixelBuffer;    outBuffer.width = CGImageGetWidth(img);    outBuffer.height = CGImageGetHeight(img);    outBuffer.rowBytes = CGImageGetBytesPerRow(img);            // 第三个中间的缓存区,抗锯齿的效果    void *pixelBuffer2 = malloc(CGImageGetBytesPerRow(img) * CGImageGetHeight(img));    vImage_Buffer outBuffer2;    outBuffer2.data = pixelBuffer2;    outBuffer2.width = CGImageGetWidth(img);    outBuffer2.height = CGImageGetHeight(img);    outBuffer2.rowBytes = CGImageGetBytesPerRow(img);        //Convolves a region of interest within an ARGB8888 source image by an implicit M x N kernel that has the effect of a box filter.    error = vImageBoxConvolve_ARGB8888(&inBuffer, &outBuffer2, NULL, 0, 0, boxSize, boxSize, NULL, kvImageEdgeExtend);    error = vImageBoxConvolve_ARGB8888(&outBuffer2, &inBuffer, NULL, 0, 0, boxSize, boxSize, NULL, kvImageEdgeExtend);    error = vImageBoxConvolve_ARGB8888(&inBuffer, &outBuffer, NULL, 0, 0, boxSize, boxSize, NULL, kvImageEdgeExtend);            if (error) {        NSLog(@"error from convolution %ld", error);    }        //    NSLog(@"字节组成部分：%zu",CGImageGetBitsPerComponent(img));    //颜色空间DeviceRGB    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();    //用图片创建上下文,CGImageGetBitsPerComponent(img),7,8    CGContextRef ctx = CGBitmapContextCreate(                                             outBuffer.data,                                             outBuffer.width,                                             outBuffer.height,                                             8,                                             outBuffer.rowBytes,                                             colorSpace,                                             CGImageGetBitmapInfo(image.CGImage));        //根据上下文，处理过的图片，重新组件    CGImageRef imageRef = CGBitmapContextCreateImage (ctx);    UIImage *returnImage = [UIImage imageWithCGImage:imageRef];        //clean up    CGContextRelease(ctx);    CGColorSpaceRelease(colorSpace);        free(pixelBuffer);    free(pixelBuffer2);    CFRelease(inBitmapData);        CGColorSpaceRelease(colorSpace);    CGImageRelease(imageRef);        return returnImage;}