| 摘要 |
PURPOSE:To decrease the number of times of processings by coding gradation information comprising both an average gradation of a light group and the average gradation of a dark group to eliminate the need for the averaging processing depending on the area ratio to blocks in a binary image region. CONSTITUTION:A halftone image signal 1 is inputted to a P0 calculation section 3 and a latch circuit 2 in the unit of blocks, and the P0 calculation section 3 at the point of time of input for one block completes the calculation of the average gradation P0 of the said block. The average gradation P0 is compared with each element in the said block by a comparator 4 and the result of comparison is outputted as resolution information from the comparator 4. A P1 calculation section 6, a P2 calculation section 7, a P2(max) calculation section 8 and a P2(min) calculation section 9 calculate respectively an average gradation P1, an average gradation P2, the maximum and minimum gradation P2(max), P2(min) from the resolution information. A gradation information decision section 10, based on the said information, decides the representative average gradation (gradation information) of one or two kinds at each block unit.
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