A region of {HEAD ~ an image} having a plurality of {TAIL ~ corresponding image values} is encoded to generate a temporary encoded region 
A region of { HEAD ~ an image } having a plurality of { TAIL ~ corresponding image values } is encoded to generate a temporary encoded region
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH