Blue-Noise Multitone Dithering

Abstract

The introduction of the blue-noise spectra-high-frequency white noise with minimal energy at low frequencies-has had a profound impact on digital halftoning for binary display devices, such as inkjet printers, because it represents an optimal distribution of black and white pixels producing the illusion of a given shade of gray. The blue-noise model, however, does not directly translate to printing with multiple ink intensities. New multilevel printing and display technologies require the development of corresponding quantization algorithms for continuous tone images, namely multitoning. In order to define an optimal distribution of multitone pixels, this paper develops the theory and design of multitone, blue-noise dithering. Here, arbitrary multitone dot patterns are modeled as a layered superposition of stack-constrained binary patterns. Multitone blue-noise exhibits minimum energy at low frequencies and a staircase-like, ascending, spectral pattern at higher frequencies. The optimum spectral profile is described by a set of principal frequencies and amplitudes whose calculation requires the definition of a spectral coherence structure governing the interaction between patterns of dots of different intensities. Efficient algorithms for the generation of multitone, blue-noise dither patterns are also introduced.

Tone-Replacement Error Diffusion for Multitoning

“…In addition, comparisons among the proposed method and the following methods are provided: 1) M-DBS: DBS for multitoning [12], adopting the normalized circular-symmetrical Gaussian filter of size 7 × 7 and standard deviation of 1. 2) M-BN: Blue-noise multitoning [13], adopting the first concentration for 3-level in their study, and the concentrations for other q-level are generated using M-DBS single tone patterns. 3) M-OD: Ordered dithering for multitoning with overmodulation using dither array [15] of size 32 × 32.…”

“…Nonetheless, since the DBS can generate excellent halftones, it has been extended to design the dithering matrix [11]. Moreover, DBS-extended multitoning has also been proposed in [12] and [13] recently, and the designed dithering matrix has also been incorporated with the OD for multitoning [12], [14].…”

Visual Cryptography Using Computation-Free Bit-Plane Reconstruction

“…Multilevel halftoning converts a grayscale image into an image with a smaller number of levels. Typical algorithms include multilevel error diffusion [16,17] and multilevel dithering [18]. Multilevel halftoning is an extension of binary halftoning [19][20][21][22][23].…”

Dot-Diffused Halftoning With Improved Homogeneity

“…In general, the properties of halftones can be categorized into blue-or green-noise to render the frequency of dot appearance for various printers. For instance, inkjet printers exploit the advantage of blue-noise halftoning for a better illusion of a given shade of color [2]. Conversely, laser printers lean to consider green-noise halftoning, because of the unstable printed dots induced by the electrophotography printing process [3].…”