Abstract

Ordered dither has long been considered to be a simple and effective method of image binarization. If f_t is the two-dimensional continuous signal to be halftoned, then ordered dither consists of thresholding the discrete space signal f_n against a periodic spatial screen σ_n whose periodicity is defined by a periodicity matrix N. Although in some dithering schemes used in practice, N is not assumed to be a diagonal matrix, most theory on dithering does include this assumption. Consequently, the majority of optimal dither patterns are designed for rectangularly periodic screen functions. In this paper the benefits of altering N are analyzed in an effort to improve the ordered dither algorithm. Optimal dither patterns for several representative nonrectangular screen periodicities are derived. It is shown that the optimal pattern sequences for these periodicities have gray-scale-rendition capabilities superior to those of previously considered dither patterns, resulting in substantially improved image fidelity.

© 1988 Optical Society of America

Halftone patterns for arbitrary screen periodicities: errata

Tandhoni S. Rao and Gonzalo R. Arce
J. Opt. Soc. Am. A 7(2) 326-326 (1990)

Digital halftoning technique using a blue-noise mask

Theophano Mitsa and Kevin J. Parker
J. Opt. Soc. Am. A 9(11) 1920-1929 (1992)

Minimizing stochastic moiré in frequency-modulated halftones by means of green-noise masks

Daniel L. Lau, Arif M. Khan, and Gonzalo R. Arce
J. Opt. Soc. Am. A 19(11) 2203-2217 (2002)

Multiresolution, error-convergence halftone algorithm

Eli Peli
J. Opt. Soc. Am. A 8(4) 625-636 (1991)

Fourier spectra of digital halftone images containing dot-position errors

Paul W. Melnychuck and Rodney Shaw
J. Opt. Soc. Am. A 5(8) 1328-1338 (1988)