1. An image forming apparatus for forming a two-dimensional bar code, the image forming apparatus comprising: a storage unit configured to store a plurality of types of particular shape images, each of the particular shape images configures the two-dimensional bar code; an image forming unit configured to form a measurement pattern image for measurement, which includes one or more of the particular shape images, upon an image carrier, as a developing material image; a pattern reading unit configured to read the measurement pattern image that is formed upon the image carrier; a first determination unit configured to determine a difference between a shape of the particular shape image that is included in the measurement pattern image that is read with the pattern reading unit, and a shape of the particular shape image that is stored in the storage unit; and a second determination unit configured to determine an image forming condition with regard to the particular shape image stored in the storage unit, in accordance with the difference that is determined by the first determination unit.