| 摘要 |
PROBLEM TO BE SOLVED: To realize an artificial halftoning excellent in gray scale presentation by an error diffusing method. SOLUTION: After accumulated errors from peripheral pixels are added at an error adding section 61, image data is quantized at a quantizing section 63. A quantization error is operated at an error operating section 64 and distributed at an error distributing section 66 to unquantized pixels on the periphery. A parameter generating section 51 imparts variation threshold values V1-V3 varying periodically in the two-dimensional direction to the quantizing section 63. The variation threshold values V1-V3 become V1<V2<V3 for pixels corresponding to the vicinity of col point or vertex of periodic variation, and the quantizing section 63 performs teradic processing. The variation threshold values V1-V3 become V1=V2=V3 for other pixels and the quantizing section 63 performs binary processing. Consequently, dots are formed by periodic variation of the variation threshold values V1-V2 and pixels constituting the circumferential fringe of the dots are subjected to teradic processing.
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