Peking University

Beijing Founder Electronics Co., Ltd.

Shixiong Ma

Bin Yang

Haifeng Li

Lidong Wang

An image processing method includes: generating a stochastic screening dither matrix (S); performing a centered positive-negative conversion operation on the stochastic screening dither matrix (S); generating a screen dot dither contrast matrix for each color surface according to the stochastic screening dither matrix after being subjected to the positive-negative conversion operation and a stochastic screening dither threshold set for each color surface of an image; performing a logical 'and' operation between each data item in a one-bit amplitude modulation screen dot matrix of each color surface of the image and a data item at a corresponding position in the screen dot dither contrast matrix of the color surface, and using a result as a processed value of a corresponding data item in the one-bit amplitude modulation screen dot matrix of the color surface. An apparatus corresponding to the image processing method is also provided. According to the above-described image processing method and apparatus, the problem in the prior art of an excess of pure-color pixels existing in an original one-bit dot matrix can be resolved.

Image processing method and apparatus

The present invention relates to a method for producing halftone dots in the field of image hard copying, more particularly to a method for frequency-modulation screening using error diffusion based on dual-feedback. In the known frequency-modulation and amplitude-modulation screening technology, it is hard to output a halftone image with high quality using an output equipment with a low resolution (600 dpi) and the satisfactory effect of representing the gradations of the original image in detail and holding the smoothness of the original image can not be achieved. By using the dual-feedback technology based on a basic algorithm of the error distribution, the method in the present invention realizes the organic combination of the conventional frequency-modulation and amplitude-modulation screens and achieves the effect of mixed screening. The method in the present invention can effectively solve the problem of losing gradations of dots in an output equipment with low resolution and can reduce the moire caused by the random distribution characteristic so as to output halftone images with high quality and full gradations.

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Beijing, China

Shixiong Ma