The Optimization of the Template and Study of State Reduction in Table Look-Up Method of Inverse Halftoning for Error Diffused Images

Abstract

Various methods have been proposed for Inverse Halftoning (IH) of Error Diffusion (ED) Images. Among them Table Look-Up method based on every possible combination of the bi-level output of reference pixels has been considered to be most effective and quite practical since IH function can be generated by simple averaging of the histogram of original con-tone levels of the target pixels in each context, and the image quality can be controlled by the number of reference pixels. In this paper, we will optimize the reference template and propose a hybrid system, in which each context is composed of the combination of the conventional logic pattern of prioritized reference pixels and the number of black pixels among other reference pixels. The result showed that the SNR compared under the same number of contexts is found to be improved from the conventional method especially when applied to the images not included in the training data.