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