the printing operation of an ink jet printer is controlled based on the density of the image to be printed . using the density , a required drying time for each swath of printed matter is determined based on the image density . also using the density , a maximum print frequency of firing the ink jets is determined . the density is determined by filtering stored print data by dividing the print data into blocks and determining a maximum number of on pixels in a block . such filtering enables clusters of on pixels to be detected thus providing a more accurate determination of the density .