UIGraphicsBeginImageContext with parameters

I am taking a screenshot in my application. I am able to take the screenshot.

Now I want to take the screenshot by specifying the x and y coordinate. Is that possible?

UIGraphicsBeginImageContext( self.view.bounds.size );
[self.view.layer renderInContext:UIGraphicsGetCurrentContext(  )];
UIImage* aImage = UIGraphicsGetImageFromCurrentImageContext(  );