Zuschneiden eines Bildes mit Rechteckiger Kasten der ausgewählte Bereich?

einige änderungen in der button-Aktion

-(IBAction) cropImage:(id) sender{


        //Create rectangle that represents a cropped image  
        //from the middle of the existing image

    float xCo,yCo;

    float width=bottomCornerPoint.x-topCornerPoint.x;

    float height=bottomCornerPoint.y-topCornerPoint.y;


    if(width<0)

    width=-width;


    if(height<0)

        height=-height;


    if(topCornerPoint.x <bottomCornerPoint.x)

    {

    xCo=topCornerPoint.x;

    }

    else 
    {
            xCo=bottomCornerPoint.x;
        }


        if(topCornerPoint.y <bottomCornerPoint.y)

    {

            yCo=topCornerPoint.y;

        }


    else {

            yCo=bottomCornerPoint.y;

        }


        CGRect rect = CGRectMake(xCo,yCo,width,height);

        //Create bitmap image from original image data,
        //using rectangle to specify desired crop area

        UIImage *image = [UIImage imageNamed:@"abc.png"];


        CGImageRef imageRef = CGImageCreateWithImageInRect([image CGImage], rect);

        UIImage *img = [UIImage imageWithCGImage:imageRef]; 

        CGImageRelease(imageRef);


        //Create and show the new image from bitmap data

        imageView = [[UIImageView alloc] initWithImage:img];

        [imageView setFrame:CGRectMake(110, 600, width, height)];

        imageView.image=img;

        [[self view] addSubview:imageView];

        [imageView release];



    }