Image processing method and apparatus

Abstract

An image processing method and an image processing apparatus are provided for maintaining image quality through simple processing while reducing the number of gradation levels of image data by error diffusion processing. In an image processing apparatus, data outputted from a filter is subtracted from input image data x(i, j) at a first subtracter. Data outputted from the subtracter is quantified at a quantifier. Data outputted from the quantizer is outputted as output image data y(i, j). Furthermore, the data outputted from the subtracter is subtracted from the data outputted from the quantizer at a second subtracter to produce quantization error e0(i, j). At a quantization error converter, quantization error e0(i, j) is converted into quantization error e1(i, j) within a specific range determined for each quantization level, based on the quantization level after quantization at the quantizer. Quantization error e1(i, j) is inputted to the filter. Data outputted from the filter is inputted to the first subtracter.

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