Importance

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Abstract

An image processing apparatus such as a digital printer or digital facsimile apparatus for half tone processing input image data has: an input device to input image data indicative of a concentration of an image; a discriminating circuit to discriminate whether the input image data is smaller than a threshold value or not; a binarizing circuit to binarize the input image data into binary data of high and low levels; and a setting circuit to set the binary output of the image data to the low (0) level irrespective of the result of the binarization by the binarizing circuit when the input image data is determined to be smaller than the threshold value. The input device includes a reading circuit to read the original image and a generator to generate image data indicative of the original image concentration. When the pixel concentration to be processed by an error diffusion method is smaller than the threshold value, the error data generated for that pixel is set to 0, with the result that particles-like noises in the high contrast portion are eliminated and the encoding efficiency in highlight portions is improved. Thus, a high quality image of excellent resolution and gradations can be transmitted at a high speed.

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