| 摘要 |
PURPOSE:To estimate an excellent intermediate tone picture by preparing plural kinds of the scanning aperture with different open area and selecting a density pattern discriminating circuit and a conditional equation discrimination depending on the spatial frequency component of a picture. CONSTITUTION:Plural kinds of scanning aperture being regions set in calculating an intermediate tone level are prepared, and a scanning aperture larger than the referenced scanning opening is selected in case of the low spatial frequency region, that is, in case of a picture such as gradation picture. In this case, which scanning aperture is to be selected depends on whether or not a conditional equation representing no density change in a region to be discriminated is satisfied by using the conditional equation discrimination circuit 70. Thus, in case of a high spatial frequency region, that is, in case of a picture such as a line picture or character picture, a scanning aperture smaller than the reference scanning aperture is selected. Which scanning aperture is to be selected depends on whether or not a condition representing the absence of the change in the density pattern in the region to be discriminated is satisfied by using the density pattern discrimination circuit 60. Thus, an intermediate tone picture close to an original picture is estimated.
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