Multilevel halftoning using a randomised Bayer matrix.

摘要

A reproduction method for continuous tone images on an output device having multilevel capabilities is described. The microdots addressable by the output device are arranged into identical tiles. The microdots in a tile get a sequence number, according to a randomised Bayer pattern for which the runlengths of microdots having low sequence numbers are reduced. The sequence is divided into five subsequences. The microdots belonging to the first three subsequences are changed exclusively to higher density levels for decreasing intensity levels, each within a specific intensity range of the input image. The microdots belonging to the last two subsequences are used to more continuously reproduce the image levels. Equivalent microdots within a tile are further differentiated by a second sequence numbering, in order to ensure smooth and precise average density transitions in reproduced continuous tones.