| 摘要 |
PURPOSE:To obtain a picture close to an original intermediate gradation picture by setting plural kinds of scanning opening, scanning a dither picture while selecting an optimum scanning opening at every picture element and using a count of a white picture element number in the scanning opening as an estimated halftone picture. CONSTITUTION:In a dither picture formed by a dither matrix, plural scanning openings are set to a digital binary picture stored in a storage means such as a memory, a prescribed operation processing is applied, the optimum scanning opening is selected among the said plural kinds of scanning openings at each picture element, number of white picture elements in the scanning opening selected in this way is counted to obtain an estimate value of the halftone picture. As the said prescribed operation processing, the algorithm is used, where a large opening is selected at a low space frequency region (a region with less picture element level change) and a small opening is selected at a high space frequency region. So long as no density change in the scanning opening is recognized, a larger opening is selected.
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