How to cut an image into irregular shapes using objective c - ios

Question

Thanks to everyone. I have got solution for cutting an image into irregular shapes in java. But now i want to achieved this in iOS.
Here is my requirement：
I am using fingers to select particular part by touch and draw on an image , after completing drawing, i want to draw that part of the image. I am able to draw using touches, but how can i cut that particular part?
i know cutting an image into rectangular shape and circle but not into a particular shape.
If any one know please help me.

Answer 1

Draw a closed CGPath and turn it into an Image Mask. If I had more experience I'd give more details, but I've only done the graphs in a weather app. A guide should help.

Answer 2

Bellow is the code for corp image with selected rectangle area. But you can customized your selected area with CGPath and then corp the image.
-(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];
}

Answer 3

CGSize newSize = CGSizeMake(backGroundImageView.frame.size.width, backGroundImageView.frame.size.height);
UIGraphicsBeginImageContext(newSize);
[<Drawing Imageview> drawInRect:CGRectMake(0,0,newSize.width,newSize.height)];
[backGroundImageView.image drawInRect:CGRectMake(0,0,newSize.width,newSize.height) blendMode:kCGBlendModeSourceIn alpha:1.0];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();