Expansion and Implementation of a 3x3 Sobel and Prewitt Edge Detection Filter to a 5x5 Dimension Filter


Sobel and Prewitt edge detection is considered in this work. Technically Sobel operator is a discrete differentiation operator computing an approximation of the gradient of the image intensity function. The result of the Sobel operator is either the corresponding gradient vector or the norm of this vector. The Prewitt operator gives values that are symmetric around the center (x,y), while Sobel operator gives weight to point lying closer to (x,y). The horizontal and vertical gradient matrices whose dimensions are 3x3 for Sobel and Prewitt method has been generally used in edge detection operation. In this paper, the standard 3x3 dimension Sobel and prewitt masks, which are based on the relationship between point in the Cartesian grid and its 8 neighbors where the gradient value represent the sum of two orthogonal values, is expanded to find edges using the matrices whose dimension are 5x5 and these matrices are applied on images using Matlab.