This article proposes a halftoning method using dispersed CMY dithering with blue noise masks (BNM) to print CMY dots instead of black (K) dots in a bright gray region in a black-and-white (B/W) image. To reduce high granularity in a bright region, dispersed CMY dots using a BNM instead of K dots are spatially assigned to a bright region. First, a threshold is determined to avoid the granularity caused by K dots. Below this threshold, the image made by the BNM is composed of CMYK dots, whereas above the threshold, a dispersed CMY image is made from mutually exclusive C, M, and Y patterns, defined by the stacking constraint of the BNM. To make mutually exclusive C, M, and Y patterns, modified jointly-blue noise masks (MJBNMs) are generated for a grayscale image. As a result of processing a grayscale image, the low-pass filtered error for single and triple patterns where the three mask patterns overlap is minimized. As such, single and triple patterns are used. Experiments demonstrated that the bright regions produced by the proposed method were uniform and sufficiently pleasing when compared to conventional results.
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