Properties of jointly-blue noise masks and applications to color halftoning

With the emergence of blue noise halftoning as a preferred halftoning techn ique, the issues of Moire patterns in conventional ordered dither color hal ftoning are replaced by new issues concerning the quality of overlaid blue noise patterns. The goal of blue noise mask design in color halftoning is t o generate a set of blue noise masks that produce high quality blue noise p atterns whether they are used individually or jointly. We first address thi s question by inspecting various combinations of unstructured binary patter ns, then explore the elementary properties of combinations of blue noise bi nary patterns. Based on the above analysis, an algorithm using filter techn iques is proposed. This algorithm generates a set of jointly blue noise mas ks (JBNM) and each mask of the JBNM will be applied to one color plane. The JBNM possesses the properties such that each individual mask is blue noise , also the combination of the masks produce color images with blue noise ch aracteristics, e.g., the dots from different color planes are mutually excl usive and maximally dispersed at highlight levels. Examples of halftoned co lor patches using JBNM and other schemes are illustrated. The evaluation de monstrates that JBNM can produce high quality color halftone patterns with little texture and graininess.