1. An image generating apparatus employing an electrophotographic method for generating an image by performing area coverage modulation to express a halftone color according to a gross area of dots displayed in a pixel of the image, the image generating apparatus comprising: a control unit configured to generate the image, in response to receiving a pixel gradation instruction, in such a manner that the halftone color is expressed with a selected one of dither patterns corresponding to respective predetermined densities, each of the densities being determined by gross areas of dots calculated in view of shapes of the dots.