| 摘要 |
PURPOSE:To obtain 1/2-reduced picture data without spoiling gradation characteristics by switching an extracted picture element position to an even digit and an odd digit on coordinates alternately at every sequential dither matrix position in an original picture data area, and extracting and selecting picture elements. CONSTITUTION:Extracted picture elements are alternated at every sequential dither matrix position in picture data areas corresponding to four dither matrixes which are arranged in a 2X2 array to extract pictures shown by a circle mark. An X and an Y address for extracting a picture element from an original picture data area are generated by simple address calculation or by using a conversion table. When 1/2 reduction processing is performed by this method, the number of gradations is the same with an original picture, and the picture is reduced to half uniformly in every gradation, so tha mean brightness on a screen when the picture is displayed is the same with the original picture.
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