Reduction of the displacement of the error diffusion patterns by means of programmable thresholds disturbance

摘要

PROBLEM TO BE SOLVED: To provide a process for removing a pattern shift artifact in a printed image by perturbing relation between a threshold and an image signal value. ;SOLUTION: The proposed process uses a programmable multilevel gray signal modifying circuit for modifying a multilevel gray signal only by a prescribed value in accordance with its gray level. The modified multilevel gray signal is binarized to a binary pixel signal in accordance with a relation between the modified multilevel gray signal and a threshold. The process generates an error corresponding to the relation and diffuses the error to adjacent pixels. The multilevel gray signal is modified by any random noise multiplied by a gray level dependent coefficient or a prescribed value from a checker board-like or vertical line-like pattern. The value from the pattern depends upon the pixel position of the image data or the gray level.;COPYRIGHT: (C)1996,JPO