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