1. An image forming device comprising: an input unit for input of dot information concerning size of dots in an image; a memory unit storing a test pattern and information relating a reference density to the dot information; an image forming unit for forming an image of the test pattern stored in the memory unit according to the dot information input by the input unit; a density detector for detecting a density of the image formed by the image forming unit; and a processing unit for obtaining the reference density corresponding to the dot information input by the input unit from the information stored in the information memory unit, performing a comparison of the reference density with the density detected by the density detector, and adjusting a parameter that controls the density of the image formed by the image forming unit according to a result of the comparison.