I want to take an image in which there will be a quadrilateral, and skew or otherwise distort the entire image such that the object that was a quadrilateral is now a square or rectangle. I realize this will distort the image, and that is okay. I know how to skew or manipulate an image, but I can't conceptualize how this would be done given information regarding the coordinates of the four points that define the corners of a quadrilateral within the image itself. I can safely find those coordinates every time, so that part is a given. This is for an experimental iPhone app. Any help would be much appreciated.