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