 The Prewitt operator was developed by Judith M. S. Prewitt.In simple terms, the operator calculates the "gradient" of the image intensity at each point, giving the direction of the largest possible increase from light to dark and the rate of change in that direction.The result therefore shows how "abruptly" or "smoothly" the image changes at that point, and therefore how likely it is that part of the image represents an "edge", as well as how that edge is likely to be oriented.