Non-Photorealistic Computer Graphics Library

Special Effects with Half-Toning

Author(s): John W. Buchanan.
Article: Computer Graphics Forum, Vol. 15, No. 3, pp. 97--108, 1996.
[BibTeX]

Abstract:
Half-toning is the process by which gray-scale images are approximated with sets of black and white pixels. The process works because our eyes perceive a local average, thus half-toning seeks to approximate the local average. Ideally this approximation should be accomplished without introducing ‘undesirable' artifacts. In many situations the stylized display of images is desired. Often this stylized display is accomplished by the addition of semi-structured artifacts. In current applications the designer processes the image using tools provided by some image processing package. The resulting image is then half-toned and printed. Half-toning these processed images can reduce the visual impact of the special effects that have been introduced in the image. In this paper we show that the processes of controlled artifact introduction and half-toning can successfully be combined. By combining these two processes we ensure that the printed image is what the designer intended. We present a brief overview of the current error-diffusion half-toning techniques. We then propose several ways in which artifacts can be introduced to the image. This discussion is accompanied by a set of illustrative images. In particular, we discuss the introduction of false edges and the alteration of the scan pattern. We illustrate these techniques with a variety of images. We conclude the paper with a discussion on these new half-toning methods for the generation of binary gray-scale textures. In addition to showing how to generate these binary gray-scale textures we also show how these gray-scale textures can be used to half-tone images.