Dither pattern generating apparatus for generating dither pattern corrected for density change accompanying deterioration with time

Abstract

In a printer which corrects a density change by measuring densities of a plurality of output dither patterns (test patterns) by a sensor and obtaining a γ characteristic curve, the following processes are performed. Data of the present number of print sheets is obtained from a print sheet counter in the printer. On the basis of the obtained data, a proper sensor density curve is selected. A sensor value obtaining unit obtains density data of a generated test pattern. On the basis of the selected sensor density curve and the obtained density data, a γ characteristic curve is calculated. A dither pattern is generated based on the γ characteristic curve.