iphone中模糊图片的指定区域

把下面的Pangesture添加到view或者imageview中：

UIPanGestureRecognizer *panGesture=[[UIPanGestureRecognizer alloc]initWithTarget:self action:@selector(imageTaped:)];
[panGesture setMaximumNumberOfTouches:1];
[self.view addGestureRecognizer:panGesture];

模糊图片的方法

- (void)imageTaped:(UIPanGestureRecognizer *)gestureRecognizer
{

    CIContext *context = [CIContext contextWithOptions:nil];
    CGPoint touchLocation = [gestureRecognizer locationInView:self.imgviewMain];


    CGRect temp=CGRectMake(touchLocation.x-25, ((self.imgviewMain.frame.size.height-50) - touchLocation.y)+25, 50, 50);

    CIImage *inputImage0 = [[CIImage alloc] initWithImage:self.imgviewMain.image];

    CIImage *inputImage = [[CIImage alloc] initWithImage:[UIImage imageWithCGImage:[context createCGImage:inputImage0 fromRect:temp]]];
    CIFilter *blurFilter = [CIFilter filterWithName:@"CIGaussianBlur"];
    [blurFilter setDefaults];
    [blurFilter setValue: inputImage forKey: @"inputImage"];
    [blurFilter setValue: [NSNumber numberWithFloat:0.1]
                  forKey:@"inputRadius"];


    CIImage *outputImage = [blurFilter valueForKey: @"outputImage"];
    UIImageView *imgtest=[[UIImageView alloc]init];

    imgtest.image=[UIImage imageWithCGImage:[context createCGImage:outputImage fromRect:outputImage.extent]];



    UIImage *image;

    UIImage *bottomImage = self.imgviewMain.image; 
          image = imgtest.image;    


    CGSize newSize = CGSizeMake(self.imgviewMain.frame.size.width, self.imgviewMain.frame.size.height);
    UIGraphicsBeginImageContext( newSize );

    [bottomImage drawInRect:CGRectMake(0,0,768,1024)];

    CGRect newRect2=CGRectMake(temp.origin.x,((self.imgviewMain.frame.size.height-50) - temp.origin.y), image.size.width, image.size.height);
    image=[self makeRoundedImage:image radius:10];

    [image drawInRect:newRect2 blendMode:kCGBlendModeNormal alpha:0.5];
     UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    self.imgviewMain.image=newImage;
   }
RoundedImage Method

-(UIImage *)makeRoundedImage:(UIImage *) image
                      radius: (float) radius;
{
    CALayer *imageLayer = [CALayer layer];
    imageLayer.frame = CGRectMake(0, 0, image.size.width, image.size.height);
    imageLayer.contents = (id) image.CGImage;

    imageLayer.masksToBounds = YES;
    imageLayer.cornerRadius = radius;

    UIGraphicsBeginImageContext(image.size);
    [imageLayer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *roundedImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return roundedImage;
}