Image signal processer reproducing halftone images in a recording system printed thickened or thinned dots

摘要

An error distribution type image signal processor has a preprocessing unit consisting of a spatial filter for preprocessing input image signals of pixels, a recording dot correction factor setter for setting a correction factor based on a difference between an actual dot size and a theoretical dot size, an output image memory for storing output image signals obtained by binarizing the input image signals preprocessed, an error data corrector for correcting error data defined as a difference between the input image signals preprocessed and the output image signals binarized according to the correction factor and the output image signals binarized, an error data memory for storing corrected error data output from the error data corrector, and an error filter for weighting the corrected error data of pixels adjoining a pixel of interest and adding the corrected error data to an input image signal of the pixel of interest. Therefore, the error data are precisely corrected, and a halftone image with a smooth gradation is reproduced in a wide tonal range.