iOS view模糊背景

/**
 *  模糊背景
 *
 *  @param image    需要模糊的图片
 *  @param blur     高斯模糊的值
 *
 *  @return
 */
- (UIImage *)blurryImage:(UIImage *)image withBlurLevel:(CGFloat)blur
{
    if ((blur < 0.0f) || (blur > 1.0f)) {
        blur = 0.5f;
    }
    
    int boxSize = (int)(blur * 100);
    boxSize -= (boxSize % 2) + 1;
    
    CGImageRef img = image.CGImage;
    
    vImage_Buffer inBuffer, outBuffer;
    vImage_Error error;
    void *pixelBuffer;
    
    CGDataProviderRef inProvider = CGImageGetDataProvider(img);
    CFDataRef inBitmapData = CGDataProviderCopyData(inProvider);
    
    inBuffer.width = CGImageGetWidth(img);
    inBuffer.height = CGImageGetHeight(img);
    inBuffer.rowBytes = CGImageGetBytesPerRow(img);
    inBuffer.data = (void*)CFDataGetBytePtr(inBitmapData);
    
    pixelBuffer = malloc(CGImageGetBytesPerRow(img) * CGImageGetHeight(img));
    
    outBuffer.data = pixelBuffer;
    outBuffer.width = CGImageGetWidth(img);
    outBuffer.height = CGImageGetHeight(img);
    outBuffer.rowBytes = CGImageGetBytesPerRow(img);
    
    error = vImageBoxConvolve_ARGB8888(&inBuffer, &outBuffer, NULL, 0, 0, boxSize, boxSize, NULL, kvImageEdgeExtend);
    
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef ctx = CGBitmapContextCreate(outBuffer.data, outBuffer.width, outBuffer.height, 8, outBuffer.rowBytes, colorSpace, CGImageGetBitmapInfo(image.CGImage));
    
    CGImageRef imageRef = CGBitmapContextCreateImage (ctx);
    UIImage *returnImage = [UIImage imageWithCGImage:imageRef];
    
    //clean up
    CGContextRelease(ctx);
    CGColorSpaceRelease(colorSpace);
    
    free(pixelBuffer);
    CFRelease(inBitmapData);
    
    CGColorSpaceRelease(colorSpace);
    CGImageRelease(imageRef);
    
    return returnImage;
}