An image forming apparatus characterized by: a first image forming section being adapted to form a first image of a white developer material on a print medium; a second image forming section being adapted to form a second image of a second developer material of a color different from white on the print medium; and a discharging section being adapted to discharge the print medium on which at least one of the first image and the second image is formed; a controller being adapted to drive at least one of the first image forming section and the second image forming section to perform printing; a determining section configured to determine in which of a first printing mode and a second printing mode an image should be formed on the print medium, the first printing mode being such that only the first image forming section forms the first image on the print medium, the second printing mode being such that the first image forming section forms the first image on the print medium and the second image forming section forms the second image on the first image so that the first image and the second image are printed one over the other; and a selector being configured to select one of a first halftone screen for the first printing mode and a second halftone screen for the second printing mode, the first halftone screen including a first number of raster lines per unit distance and being applied to the first image, the second halftone screen including a second number of raster lines per unit distance, the second number of raster lines being smaller than the first number of raster lines and being applied to the first image. a first image forming section being adapted to form a first image of a white developer material on a print medium; a second image forming section being adapted to form a second image of a second developer material of a color different from white on the print medium; and a discharging section being adapted to discharge the print medium on which at least one of the first image and the second image is formed; a controller being adapted to drive at least one of the first image forming section and the second image forming section to perform printing; a determining section configured to determine in which of a first printing mode and a second printing mode an image should be formed on the print medium, the first printing mode being such that only the first image forming section forms the first image on the print medium, the second printing mode being such that the first image forming section forms the first image on the print medium and the second image forming section forms the second image on the first image so that the first image and the second image are printed one over the other; and a selector being configured to select one of a first halftone screen for the first printing mode and a second halftone screen for the second printing mode, the first halftone screen including a first number of raster lines per unit distance and being applied to the first image, the second halftone screen including a second number of raster lines per unit distance, the second number of raster lines being smaller than the first number of raster lines and being applied to the first image.