calculating an evaluation function by means of {TAIL ~ the gray level ratio} by repeating the gray level ratio calculating {HEAD ~ step} in the specified area 
calculating an evaluation function by means of { TAIL ~ the gray level ratio } by repeating the gray level ratio calculating { HEAD ~ step } in the specified area
OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH