{HEAD ~ A black area measurement section} measures a black area S by obtaining ratio of the number of pixels satisfying Y≦Y0 in {TAIL ~ the screen} 
{ HEAD ~ A black area measurement section } measures a black area S by obtaining ratio of the number of pixels satisfying Y≦Y0 in { TAIL ~ the screen }
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL