There are different m files for different filter to use.

perwit.m:=uses window Wx=[1 0 -1 1 0 -1]/3

and Wy=Wx and then convolves this window with the image.

sobel.m:=uses window W=[1 0 -1 2 0 -2 1 0 -1]/4

lablacian.m=uses window W=[0 1 0 1 -4 1 0 1 0]

convolve.m=convolves window and image

-There are different m files for different filter to use.

perwit.m:=uses window Wx=[1 0 -1 1 0 -1 1 0 -1]/3

and Wy=Wx　and then convolves this window with the image.

sobel.m:=uses window W=[1 0 -1 2 0 -2 1 0 -1]/4

lablacian.m=uses window W=[0 1 0 1 -4 1 0 1 0]

convolve.m=convolves window and image