| 摘要 |
PURPOSE:To simplify smoothing processing for suppressing moires at a moderate cost through the use of a small capacity memory by converting the picture signal of N-bits into n-bits (N>n) and deciding picture tone based on the signal of n-bits. CONSTITUTION:If a picture is decided to be a photo, a half tone picture or a dot original with many lines, it is subjected to smoothing processing, after which dither processing is applied to it. Smoothing is executed within a range with four picture elements in a column direction (lateral direction) and two lines in a line direction (longitudinal direction), both of which are raster-scanned, and moire suppression is carried out if the number of lines exceeds that of dot lines. Out of two lines, one line employs an original picture signal read out by raster scanning, and for data showing the other line, the picture data of n-bits having already stored in order to identify picture tone is used. Here, when the data of six bits is converted into that of two-bits, its threshold is periodically changed in accordance with the position of a picture element, whereby discontinuity caused after smoothing processing is corrected.
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