ESTIMATION METHOD FOR HALFTONE PICTURE OF MULTIVALUED DITHER PICTURE

摘要

PURPOSE:To satisfactorily estimate an original halftone picture by selecting an optimum scan aperture at every picture element through the prescribed arithmetic and employing the sum of multivalued picture element levels in the aperture. CONSTITUTION:The selection sequence of scan apertures is set D C B A, in that order. The aperture D is overlapped with a ternary dither picture, and ternary-coded with the sum 24 of the multivalued picture element levels in the aperture D as a mean picture element level. Then the ternary dither picture (w) and the ternary picture (z) are not the same pattern, and the aperture D is inappropriate for a selected aperture. If the aperture C is overlapped and ternary-coded with 26 obtained by multiplying the sum 13 of the multivalued picture element levels in the aperture C by a gain two as a mean picture element level, the aperture C is also inappropriate for a selected aperture. If the aperture B is overlapped and ternary- coded with 24 obtained by multiplying the sum 24 of the multivalued picture element levels in the aperture B by a gain two as the mean picture element level, the patterns of the multivalued dither picture (w) and the ternary picture (z) do not coincide with each other, and therefore the aperture A is selected. Where the sum of the multivalued picture element levels in the aperture A and the gain of the aperture A are 6 and 4, respectively, the estimated value of the picture comes to 24.