Abstract: In an image forming apparatus, a controller performs development of toner patterns corresponding to a first halftoning method and a second halftoning method. One of the toner patterns contains first patch images for the first halftoning method, and another one contains second patch images for the second halftoning method. The controller performs development of only one out of both a first patch image (one of the first patch images) and a second patch image (one of the second patch images) if an absolute value of a difference between the number of dots in the first patch image and that in the second patch image is equal to or less than a predetermined value and an absolute value of a difference between the number of dot-level edges in the first patch image and that in the second patch image is equal to or less than a predetermined value.

Abstract: In the image forming apparatus, the partial image data for gradation adjustment is threshold conversion data of a partial image, the partial image is a part of a base pattern image with a predetermined size and does not contain any sides of the base pattern image, and the base pattern image is an image generated in an error diffusion method; and the patch image generator unit generates an image of a toner pattern by arranging the partial image of the partial image data repeatedly, and forms the toner pattern.

Abstract: An image forming apparatus has: (a) a character-area identifying unit that identifies a character area in image data, and (b) a screen processing unit that performs a screen process of an area in the image data other than the character area by using a first dot growth pattern, and performs a screen process of the character area by using a second dot growth pattern different from the first dot growth pattern.

Abstract: In an image forming apparatus, a controller performs development of toner patterns corresponding to a first halftoning method and a second halftoning method. One of the toner patterns contains first patch images for the first halftoning method, and another one contains second patch images for the second halftoning method. The controller performs development of only one out of both a first patch image (one of the first patch images) and a second patch image (one of the second patch images) if an absolute value of a difference between the number of dots in the first patch image and that in the second patch image is equal to or less than a predetermined value and an absolute value of a difference between the number of dot-level edges in the first patch image and that in the second patch image is equal to or less than a predetermined value.

Abstract: In the image forming apparatus, the partial image data for gradation adjustment is threshold conversion data of a partial image, the partial image is a part of a base pattern image with a predetermined size and does not contain any sides of the base pattern image, and the base pattern image is an image generated in an error diffusion method; and the patch image generator unit generates an image of a toner pattern by arranging the partial image of the partial image data repeatedly, and forms the toner pattern.