Therefore, {HEAD ~ produced printing data} allows {TAIL ~ the density} to be controlled to change continuously and gradually, and quality degradation caused by density variations attributable to the printing head can be less perceptible 
allows
Therefore , { HEAD ~ produced printing data } allows { TAIL ~ the density } to be controlled to change continuously and gradually , and quality degradation caused by density variations attributable to the printing head can be less perceptible
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH