Edge Detection by Homogeneity Operator

Image edge detection by applying a 3*3 homogeneity-operator mask on every pixel in an image

This produces high homogeneity value for edge pixels and low values for non-edge pixel. Finally, a user defined threshold (here by otsu's method) is applied to mark the edges in the image. It uses 8 neighbour pixels on 3*3 mask operator
Refer: A new homogeneity-based approach to edge detection using PSO
by Mahdi Setayesh, Mengjie Zhang and Mark Johnston