| 摘要 |
PROBLEM TO BE SOLVED: To process binary processing employing the dither method at a high speed by decreasing number of times of reading threshold data. SOLUTION: A binary processing means 3b uses a coordinate representing a start/end of a drawn image obtained by an edge calculation means 3a and scan line data to compare periodic data having been stored in advance in a threshold storage means 3c with gradation data given to an image drawing object for the binary processing and the result of binarization processing is cached to a binarization processing result storage means 3d. In the case that the gradation data of the image drawing object are constant and the result of binarization processing by number of scan line periods is stored in the binarization processing result storage means 3d, the binarization processing result storage means 3d repetitively uses data resulting from shifting the cached binary processing result by a shift means 3e writes them to a band buffer means 4. Thus, time-consuming reading of threshold data from the threshold storage means 3c is avoided and binary processing is executed at a high speed.
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