| 摘要 |
PROBLEM TO BE SOLVED: To prevent an unintended gap from being caused between colors in the case of printing out a multi-color image by the electrophotography system. SOLUTION: A gap between colors takes place around borders of electrostatic latent image formed on a photoreceptor drum because the border is swallowed up by an electric field and then the border is not developed by toner. In the case of conversion from 2-bit of bit map data into 8-bit data to modulate an optical signal, line memories 1-8 and a shift register group 11 are used to hold a noted picture element and its surrounding 9×9 picture elements, and when the noted picture element is at a white level and the surrounding picture elements are not all at a white level, a conversion logic circuit 14 does not convert the noted picture element into a white level, but converts it to a value corresponding to a potential not developed by toner. Thus, a prescribed potential is provided to a circumferential part of the image which is not swallowed up.
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