In this case, {HEAD ~ a density} of information in a record on the file medium undergone the data compression is different from a density of information in {TAIL ~ the original image} 
In this case , { HEAD ~ a density } of information in a record on the file medium undergone the data compression is different from a density of information in { TAIL ~ the original image }
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL