iPhone dev Stupidity 64: Crop image from image

- (UIImage*)imageByCropping: (CGRect)rect

{

UIImage * imageToCrop = self;

// convert the rect from screen coords to Quartz 2D coords

rect = CGRectMake(rect.origin.x, self.height - rect.origin.y - rect.size.height, rect.size.width, rect.size.height);

//create a context to do our clipping in

UIGraphicsBeginImageContext(rect.size);

CGContextRef currentContext = UIGraphicsGetCurrentContext();

//create a rect with the size we want to crop the image to

//the X and Y here are zero so we start at the beginning of our

//newly created context

CGRect clippedRect = CGRectMake(0, 0, rect.size.width, rect.size.height);

CGContextClipToRect( currentContext, clippedRect);

//create a rect equivalent to the full size of the image

//offset the rect by the X and Y we want to start the crop

//from in order to cut off anything before them

CGRect drawRect = CGRectMake(rect.origin.x * -1,

rect.origin.y * -1,

imageToCrop.size.width,

imageToCrop.size.height);

//draw the image to our clipped context using our offset rect

CGContextDrawImage(currentContext, drawRect, imageToCrop.CGImage);

//pull the image from our cropped context

UIImage *cropped = UIGraphicsGetImageFromCurrentImageContext();

//pop the context to get back to the default

UIGraphicsEndImageContext();

//Note: this is autoreleased

return cropped;

}