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