1. An image forming apparatus that forms an image using color material of a plurality of colors, the image forming apparatus comprising: an image forming unit that forms a test pattern on printing material using the color material of a plurality of colors; a reading unit that reads the test pattern formed by the image forming unit on the printing material; and a control unit that controls an amount of color material of each color by changing an image forming condition in accordance with a result of reading by the reading unit, wherein the image forming unit forms a mixed pattern image, as the test pattern, in which color material of a plurality of chromatic colors are used, and the control unit controls an amount of color material of a single color based on a result of reading the mixed pattern image by the reading unit.