| 摘要 |
PROBLEM TO BE SOLVED: To make an input image into halftone without damaging the feature character of an original image and to unnecessitate much arithmetic quantity increase by changing an error diffusion coefficient corresponding to each pixel in the image for each pixel. SOLUTION: A block 230 is provided with an error diffusion filter means, a block 250 is provided with a feature extracting means, a block 260 is provided with a threshold operating means, a block 270 is provided with an adaptive algorithm means and a block 280 is provided with a weight coefficient control means. Then, both feature extracting information and the quantization error information of input/output are provided, while including them with the differential norm of input/output information as a standard and by trading off both the information, a diffusion coefficient is controlled. At controlling of the error diffusion coefficient, a result (v) (n1 and n2) of feature extraction, input information (x) (n1 and n2) and output information (y) (n1 and n2) are utilized. A valueλ(n1 and n2) adjusted with respect to each pixel is multiplied to the output, for which threshold processing is applied to a diffusion filter. Thus, the error diffusion coefficient corresponding to each pixel in the image is caused to change for each pixel.
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