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