Multi-Color and Artistic Dithering
Author(s): Victor Ostromoukhov, Roger D. Hersch.
Proceedings: Computer Graphics Proceedings, Annual Conference Series, pp. 425--432,
1999.
[BibTeX] 
Abstract:
A multi-color dithering algorithm is proposed, which converts a
barycentric combination of color intensities into a multi-color nonoverlapping
surface coverage. Multi-color dithering is a generalization
of standard bi-level dithering. Combined with tetrahedral
color separation, multi-color dithering makes it possible to print
images made of a set of non-standard inks. In contrast to most previous
color halftoning methods, multi-color dithering ensures by
construction that the different selected basic colors are printed side
by side. Multi-color dithering is applied to generate color images
whose screen dots are made of artistic shapes (letters, symbols,
ornaments, etc.). Two dither matrix postprocessing techniques are
developed, one for enhancing the visibility of screen motives and
one for the local equilibration of large dither matrices. The dither
matrix equilibration process corrects disturbing local intensity
variations by taking dot gain and the human visual system transfer
function into account. Thanks to the combination of the presented
techniques, high quality images can be produced, which incorporate
at the micro level the desired artistic screens and at the macro
level the full color image. Applications include designs for advertisements
and posters as well as security printing. Multi-color dithering
also offers new perspectives for printing with special inks,
such as fluorescent and metallic inks.