Journal of Electronic Imaging • Open AccessUniform-rosette color halftoning for N-color moiré-free printing
Presented is a unique halftone geometric configuration for color halftone printing with an arbitrary number of colorants. The configuration uses a plurality of halftone screens to produce prints that are moiré free and possess uniform hexagonal periodic rosettes. Moiré-free N-color halftoning is achieved by selecting halftone frequencies from harmonics of two rosette fundamental frequencies. With such screen configurations, the interference between any halftone frequency components, fundamentals, or higher-order harmonics of different colorants is a linear integer combination of the two rosette fundamental frequencies. The linear integer combination produces a hexagonal grid of frequency components with no components lower than the rosette frequencies other than the zero-frequency component. Thus, no visible interference, or moiré, occurs within the halftone screen combinations. The observed halftone pattern is a visually pleasing, two-dimensionally uniformly repeated hexagonal rosette. The uniform-rosette configurations can be implemented using digital single-cell nonorthogonal halftone creens. The uniform-rosette method can be used with conventional cyan-magenta-yellow-black halftone printing or with printing systems that require a relatively large number of halftone screens. The additional screens can be used for enhanced printing applications, such as printing with high-fidelity colorants, light colorants, or special colorants, such as white, metallic, and fluorescent.