Slicing UIImage into triangles in iPhone app

I am working on a iPhone app where I take a picture with the camera. Hereafter it should be possible to slice the image in various shapes - most important triangles. Can anyone give me a point in the right direction or examples etc. I have made it possible to slice into squares but not triangles.

(Updated)For creating the squared slices I used the following code snippets

CGRect ClippedRect= CGRectMake(0, 150, 320.0, 230.0);//example numbers
CGImageRef ima开发者_开发百科geRef = CGImageCreateWithImageInRect([OriginalUIImage CGImage], ClippedRect);
UIImage *resultUIImage=[[UIImage alloc]initWithCGImage:imageRef];

All help is appreciated

Regards

SOLVED:

I went with the method of masking the uiimage. So the strategy is that 1. Take picture from camera and scale. 2. Let the user draw a figure in a uiimageview and fill it with black color and the create a UIImage from this. 3. Mask the image from the camera with the user generated image. For masking the image I use the following method from http://www.developers-life.com/resize-and-mask-an-image.html

- (UIImage*) maskImage:(UIImage *)image  {

 CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();

 UIImage *maskImage = [UIImage imageNamed:@"mask.png"];
 CGImageRef maskImageRef = [maskImage CGImage];

 // create a bitmap graphics context the size of the image
 CGContextRef mainViewContentContext = CGBitmapContextCreate (NULL, maskImage.size.width, maskImage.size.height, 8, 0, colorSpace, kCGImageAlphaPremultipliedLast);


 if (mainViewContentContext==NULL)
      return NULL;

 CGFloat ratio = 0;

 ratio = maskImage.size.width/ image.size.width;

 if(ratio * image.size.height < maskImage.size.height) {
      ratio = maskImage.size.height/ image.size.height;
 } 

 CGRect rect1  = {{0, 0}, {maskImage.size.width, maskImage.size.height}};
 CGRect rect2  = {{-((image.size.width*ratio)-maskImage.size.width)/2 , -((image.size.height*ratio)-maskImage.size.height)/2}, {image.size.width*ratio, image.size.height*ratio}};


 CGContextClipToMask(mainViewContentContext, rect1, maskImageRef);
 CGContextDrawImage(mainViewContentContext, rect2, image.CGImage);


 // Create CGImageRef of the main view bitmap content, and then
 // release that bitmap context
 CGImageRef newImage = CGBitmapContextCreateImage(mainViewContentContext);
 CGContextRelease(mainViewContentContext);

 UIImage *theImage = [UIImage imageWithCGImage:newImage];

 CGImageRelease(newImage);

 // return the image
 return theImage;

}

Thank you for all the help

Try something like this:
http://iosdevelopertips.com/cocoa/how-to-mask-an-image.html
Simply make a black image as your mask and apply it to the image, if i get this explanation right.

You should be able to use this approach: Create a new image using UIGraphicsBeginImageContextWithOptions (you could also use the CoreGraphics equivalent but is much more work), then create a bezier path of the shape you want, call [yourBezierPath addClip] and then draw your image in that context. You can then get the resulting image using UIGraphicsGetImageFromCurrentImageContext. Be sure to call UIGraphicsEndImageContext() afterwards. See this question for creating an image with UIGraphicsBeginImageContextWithOptions.