summing the negative of pixel values of image pixels corresponding to each of columns 2M+1 to M+2 in {HEAD ~ a row} of the edge detection filter and adding the pixel values of image pixels corresponding to each of columns M to 1 in said row of {TAIL ~ the edge detection filter} to calculate a row value for said row 
summing the negative of pixel values of image pixels corresponding to each of columns 2M+1 to M+2 in { HEAD ~ a row } of the edge detection filter and adding the pixel values of image pixels corresponding to each of columns M to 1 in said row of { TAIL ~ the edge detection filter } to calculate a row value for said row
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH