An image generating device for generating a gradation in which the color value changes from a center of the gradation through multiple areas includes an acquisition unit that acquires parameters representing a gradation pattern including the center and shape of the gradation, a symmetry judgment unit that judges whether the gradation symmetry is satisfied (condition that the shape has line symmetry or point symmetry and the gradation center is on a line symmetry axis or at the center of point symmetry), an area determination unit that determines a partial area usable for generating a whole gradation using the gradation symmetry if the gradation symmetry is judged to be satisfied, a drawing unit that draws the gradation in the partial area based on the parameters, and a gradation development unit that develops the drawn gradation into the whole gradation using the gradation symmetry.