A composite document such as a scanned magazine page usually contains a variety of content, such as, text and halftoned images. Different kinds of content on a page have different spatial and color characteristics that are best rendered by different halftone techniques. A direct application of multiple halftone techniques in a composite document can lead to disturbing boundary artifacts caused by the switching of halftone algorithms. In this paper, we present an adaptive halftone algorithm for rendering composite documents such as scanned magazine pages, on color laser printers. The method uses a combination of error diffusion and clustered-dot screening to generate an edge-preserving halftone that also has the desirable property of low noise and minimal halftoning artifacts in smooth image regions. In the presented method, narrow boundaries around image edge regions are treated as content-transition regions, in which clustered-dot screening and error diffusion are operated simultaneously. The halftone output within a transition region is controlled by the distance of the pixel to the boundary of an identified image edge. In our simulations, the proposed algorithm results in visually superior halftones.

Date Published: 18 December 2003
PDF: 9 pages
Proc. SPIE 5293, Color Imaging IX: Processing, Hardcopy, and Applications, (18 December 2003); doi: 10.1117/12.532912

Published in SPIE Proceedings Vol. 5293:
Color Imaging IX: Processing, Hardcopy, and Applications
Reiner Eschbach; Gabriel G. Marcu, Editor(s)