Easy image cropping with core graphics

CGImageCropping.m

//The image to be cropped
UIImage *image;
//The rect to which the image is going to be cropped
CGRect croppedRect = CGRectMake(0, 0, 40, 40);
//A simple call to Core Graphics function
CGImageRef img = CGImageCreateWithImageInRect(image.CGImage, croppedRect);

//There goes the cropped image
UIImage *result = [[UIImage alloc] initWithCGImage:img] autorelease];