For a dither matrix used when converting multivalued data into image data for an output apparatus, thresholds are set such that a first dot and a second dot alternately become larger until both of the first dot and the second dot reach a first dot size, after both of the first dot and the second dot reach the first dot size, the first dot becomes larger until the first dot reaches a second dot size while the second dot does not become larger, and, thereafter, the second dot becomes larger until the second dot reaches the second dot size while the first dot does not become larger, and after both of the first dot and the second dot reach the second dot size, the first dot and the second dot alternately become larger.

For a dither matrix used when converting multivalued data into image data for an output apparatus, thresholds are set such that: a first dot and a second dot alternately become larger until both of the first dot and the second dot reach a first dot size; after both of the first dot and the second dot reach the first dot size, the first dot becomes larger until the first dot reaches a second dot size while the second dot does not become larger, and thereafter, the second dot becomes larger until the second dot reaches the second dot size while the first dot does not become larger; and after both of the first dot and the second dot reach the second dot size, the first dot and the second dot alternately become larger.

An image forming apparatus includes a first image forming section capable of forming a brilliant developer image, a second image forming section including at least one image forming section capable of forming a black developer image, a transfer section capable of transferring the brilliant developer image and the black developer image onto a medium, and a controller that controls operation of the first image forming section and the second image forming section according to received print data. When forming a brilliant image based on the print data, the controller performs control to form the brilliant image in which relative position between the brilliant developer image and the black developer image is changed depending on a medium type.