1. A printing apparatus that performs printing on a print medium, comprising: a dot data generator that performs a halftone process on image data representing a tone value of each of pixels constituting an original image to determine a status of dot formation on each of print pixels of the print image to be formed on the print medium, for generating dot data representing the determined status of dot formation, and a print image generator that forms a dot on each of the print pixels for generating a print image according to the dot data, wherein the print image is formed by mutually combining print pixels belonging to each of a plurality of pixel position groups for which a physical difference is assumed at a formation of dots by the print image generator, in a common print area, and the halftone process is configured to determine the status of dot formation on each of the print pixels on an assumption of the physical difference.