| 摘要 |
<p>A halftone screening method includes a method of moiré suppression, in which the input image is first screened in a trial screening module. The input image is then subtracted from the trial screened image to produce an error image which contains both the trial screen pattern and the moiré pattern introduced by the trial screening process. The error image is filtered in a lowpass filter to remove the trial screen pattern, leaving only the moiré pattern, which is then subtracted from the input image to produce a compensated image. Finally, the compensated image is then screened in a final screening module. The moiré image component of the comensated image tends to cancel the moiré pattern introduced by the final screening module so as to suppress moiré patterns in the final screened image. In two alternate embodiments, filter refinements are provided to reduce grayscale distortions and improve moiré suppression in the extreme light and shadow regions of the image.</p> |
