METHOD AND APPARATUS FOR REPRODUCING AN IMAGE WITH GRAY LEVEL PRINTING

摘要

A printhead forms dots of variable dot sizes grouped into cells. For each increase in cell gray level, at least one dot in the cell forms a larger dot size. Cell growth patterns are described. In a further embodiment, a gray level printer forms dots in accordance with a template corresponding to increasing cell gray levels until a line structure is stable. In another embodiment, scanned pixel values are compared to a set of thresholding values that are defined by a 4-quadrant tone reproduction analysis using a dot template, selected bit depth and dot type structure. In another embodiment, the intensity values of some pixels are modified by introducing errors to intensity values of pixels at preferred locations such that pixels along screen lines have a greater likelihood to be printed with stable dots than pixels not at such preferred locations. Errors created by modifying the intensity values are diffused to neighboring pixels. In another embodiment, contour suppression is performed on the pixels of a text or half tone region. In another embodiment said regions are printed with a higher output screen frequency. In another embodiment a descreening filter iteratively reduces a specific frequency in the digitized image.