For a display position, {HEAD ~ the user} specifies {TAIL ~ at least one subregion} of the subdivided original image 
specifies
For a display position , { HEAD ~ the user } specifies { TAIL ~ at least one subregion } of the subdivided original image
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH