obtaining as a gray level ratio {TAIL ~ a ratio} of {HEAD ~ calculation result} of the left area to calculation result of the right area 
obtaining as a gray level ratio { TAIL ~ a ratio } of { HEAD ~ calculation result } of the left area to calculation result of the right area
OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH