{HEAD ~ Means} are provided for setting {TAIL ~ the value} of the local black/white reference point for each detected constant area pixel to a calculated value for that pixel 
are provided for setting
{ HEAD ~ Means } are provided for setting { TAIL ~ the value } of the local black / white reference point for each detected constant area pixel to a calculated value for that pixel
HEAD HEAD HEAD HEAD HEAD REL REL REL REL TAIL 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