毛玻璃蒙版

应用程序毛玻璃蒙版保护账户信息（如支付宝）

先说说实现的的思路：

当程序即将进入后台时，把当前屏幕截个图，此时要将图片毛玻璃化，并作为UIImageView的image，然后将imageView放在window的最上面，等即将进入前台时移除毛玻璃蒙版。

下面就来说代码实现吧(在代理文件中实现)：

主要代码：

- (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 = 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];
}

//下面代码是 blurryImage:withBlurLeve方法l的具体实现，我将它写成了UIImage的分类，所以可以直接用UIImage调用。

//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 = 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;
}