| 摘要 |
PURPOSE:To improve a forecasting ratio by selecting only one scanning aperture of each picture element of dither picture to be forecasted and using a value obtained by binary-coding a half tone picture level based upon the selected scanning aperture as a forecasting value. CONSTITUTION:A value obtained by multiplying a picture level by gain is used as the half tone picture level of a scanning aperture B and a gradation matrix is obtained from respective levels of the half tone picture and respective thresholds of an original dither matrix. When the gradation dither matrix is compared with an original dither picture, both the patterns completely coincide with each other. Thereby, the aperture B is selected as the scanning aperture. Therefore, the aperture B is used as the one for a forecasting picture element (x), and when the half tone picture level is dithered, the dithered picture level is turned to '0', i.e. 'black', so that the forecasting picture element (x) at that time is 'black'. Provided that all picture elements included in a reference area and arranged on the outside of a dither picture are white picture elements. Consequently, the forecasting ratio can be remarkably improved.
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