| 摘要 |
PROBLEM TO BE SOLVED: To form the image of higher picture quality and to prevent increase in the capacitance of a conversion table therefor by adding the position control of a virtual dot in an image area corresponding to the gradation level of concentration as well. SOLUTION: The conversion table of a halftone processing part for electrophotography for expressing concentration gradations with dots is composed of a pattern matrix B corresponding to plural pixels in the prescribed area of a regenerative image, area look-up table (LUT) group C-1 corresponding to gradation data and the area data of virtual dots, position LUT group C-2 corresponding to the gradation data and the position data of virtual dots and further, area and position index tables D-1 and D-2 showing the correspondent spots of the LUT groups C-1 and C-2 to be referred to for the element of the matrix B. Then, the respective area and position LUT groups collect the respective data of similar virtual dots and reduce the number of tables rather than the number of elements of the pattern matrix.
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