IOS中使得图片模糊的效果的方法

-(void)blurUserView
{

    

//     DOWN_IMAGE(userView, STRING_VALUE(userDict[@"avatar_big"]), SMALL_IMAGE);
   
CIContext *context = [CIContext
contextWithOptions:nil];
   
CIImage *inputImage = [[CIImage
alloc]initWithContentsOfURL:[NSURL
URLWithString:STRING_VALUE(userDict[@"avatar_big"])]];
   
CIFilter *filter = [CIFilter
filterWithName:@"CIGaussianBlur"];
    [filter
setValue:inputImage
forKey:kCIInputImageKey];

    [filter setValue:[NSNumber
numberWithFloat:2]
forKey:@"inputRadius"];
   
CIImage *result = [filter
valueForKey:kCIOutputImageKey];

    
   
CGImageRef cgImage = [context
createCGImage:result fromRect:CGRectMake(0, -25,
180, 250)];
   
UIImage *image = [UIImage
imageWithCGImage:cgImage];
   
CGImageRelease(cgImage);
   
userView.image = image;

    
}