Objective Quality Measures , Grayscale and Color

Halftoning, the transformation from a con-tone image to a binary one, is a very important part of the printing process. The print quality is very much dependent on the characteristics of the halftoning method that was used. Finding one objective halftone image quality measure that covers all the aspects of quality is a very difficult, if not impossible, task. One of the reasons is simply the fact that you cannot judge the quality of a halftone image before it is reproduced. Therefore, the image quality is very much dependent on the application. Another reason is that some halftoning methods might work fine for certain kinds of images but produce low quality results for other images. In this paper we present two halftoning methods, one for grayscale and the other one for color images. In the color halftoning method the color separations are halftoned in a context dependent manner, which leads to high quality color halftoned images. A number of objective quality measures for grayscale and color halftoned images are introduced and discussed. Results of proposed methods and quality measures are illustrated by different examples.