Each constant area pixel is detected to be a white pixel or a black pixel and {HEAD ~ the white or black value} is set with {TAIL ~ reference} to a local black or white reference point 
is set with
Each constant area pixel is detected to be a white pixel or a black pixel and { HEAD ~ the white or black value } is set with { TAIL ~ reference } to a local black or white reference point
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH