Multiple-color image output apparatus and method which prevents a toner image on a photosensitive drum from being narrowed in the horizontal direction

摘要

When a multiple-color image is printed by electrophotography unwanted spaces are produces between different colors. These spaces are attributed to non-development of toner caused by the influence of an electric field at the boundary of an electrostatic latent image formed on a photosensitive drum. Accordingly, when data conversion is converted from two-bit data of a bitmap to eight-bit data that are used for modulating a light signal, a pixel of interest and the neighboring 9×9 pixels are stored and the state thereof is determined. If the pixel of interest is a white pixel and the neighboring pixels are all non-white pixels, then the pixel of interest is not left at a value corresponding to white, but is converted to a value corresponding to a potential that will not develop toner. The photosensitive drum is irradiated with a laser based upon the data resulting from the conversion. Thus, a sudden conversion from a potential corresponding to white to a potential corresponding to the maximum density is eliminated at the outline of the image. This makes it possible to prevent the influence of an electric field at the edge of the image and, hence, to prevent the occurrence of unwanted spaces between colors.