The filter marks sharp drops of brightness
at the original image, that means, underlines the contours of the image, almost not enhancing the noises. At the black and white image this operator shall show how quickly the brightness changes, that means, it has the greatest result where the original image changes the most quickly.
filter subtracts the image after erosion from the image after dilation. For the receiving of morphological primitive symmetric primitives are used, thus, the work of the filter only vaguely depends on the contours direction.
Size (size) parameter determines the area of the filter influence around each point.
Iterations (iteration) parameter determines the amount of iterations.