A method, apparatus, and article of manufacture provides the ability to process image data. Image data is output as picture screen elements to a display. In response to selecting a sample of the picture screen elements, a reference co-ordinate system is generated. The reference co-ordinate system is used to process each of the picture screen elements. An axis of the reference co-ordinate system defines a distance. The picture screen elements are discriminated and processed according to the distance by proportionally averaging the co-ordinates.