Patent ID: 8272707

Claim:
A printing device having a function that adjusts for deviation that occurs between ink droplet landing positions on an outbound pass and a return pass during bidirectional printing in which ink droplets of a plurality of dot sizes are discharged to print images on a print medium, comprising a print head that discharges ink droplets having a plurality of sizes; and a control unit that sets an adjustment value for said deviation for different types of images based upon a type of image being printed, a storage unit that stores adjustment values set for each dot size according to the deviation; an image buffer in which image data converted to raster data is stored; and a printing control unit that recognizes ordered dot data as a ruled line when a plurality of dots are converted in an ordered line in a direction perpendicular to the raster, determines if the number of ruled lines exceeds a predetermined threshold count in the raster direction, and controls bidirectional printing using a large-dot adjustment value stored in the storage unit when the number of ruled lines exceeds the predetermined threshold count.