1. A printing apparatus that prints an image of a first colorimetric system that is constructed with a plurality of pixels by using dots having a plurality of sizes, comprising: a print head that ejects a printing material to form the dots on a printing medium; a color conversion unit that converts the image in the first colorimetric system to an intermediate image in a second colorimetric system that can be printed by the printing apparatus; a detection unit that detects edge pixels, which constitute an edge of the intermediate image, among a plurality of pixels constituting the intermediate image; a dot allocation unit that allocates dots having a predetermined size among the dots having the plurality of sizes to the edge pixels; and a printing unit that controls the print head based on printing data indicating the dot allocation to form the image on the printing medium.