The dot diffusion method for digital halftoning has the advantage of parallelism unlike the error diffusion method. The method was improved by optimization of the so-called class matrix so that the resulting halftones are comparable to the error diffused halftones. First, 8 × 8 class matrices were used for dot diffusion method. However, there is a problem with this size of class matrix: enhancement of images is necessary before halftoning. It was found later that if the size of the class matrix was increased to 16 × 16, then there is no need for the enhancement step. In this article, we will review the dot diffusion. This will be followed by a discussion on special cases of dot diffusion. Then, we will show how the optimization is done to get the class matrices.
Murat Mese, P. P. Vaidyanathan, "Properties of Improved Dot Diffusion for Image Halftoning" in Journal of Imaging Science and Technology, 2001, pp 291 - 296, https://doi.org/10.2352/J.ImagingSci.Technol.2001.45.3.art00014