| 摘要 |
Upon gradation converting input m-bit image information into n-bit image information (m and n are integers; m>n), random numbers, the maximum values of which are changed in accordance with the input values of the m-bit image information, are generated at periods of two or more pixels, and the random numbers are selectively output while switching their signs to positive/negative within the period of two or more pixels. The output signal values and the input values of the m-bit image information are added to each other, and the sum signal values are converted into n-values by a density preservation type quantization method. With this control, the problems of sweeping, texture, and the like of the conventional density preservation type quantization method can be solved without emphasizing the granularity of an image.
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