Algorithm of hybrid screen using spiral error diffusion and threshold matrix

Abstract

To obtain optimum quality of printing, choosing right screen type to match printing workflow is vital in today conventional printing. Hybrid screen is an alternative method to achieve it. It is the combination of screens between AM and FM techniques. Hybrid screen, thus, includes the advantages of both screens. In contrast, there is an error of tone reproduction occurred at the boundary linkage of these different screen techniques. This research is aimed to eliminate this problem by generating an effective algorithm to smoothen tone at the boundary. The process based on spiral error diffusion and threshold matrix. As the result, it is found that Spiral Error Diffusion of FM screen is compatible together with threshold matrix of AM algorithm. This leads to control the area selection of hybrid screen, by which AM and FM screen boundary is variable. Besides, the area selection would create area banding between AM and FM screen in order to enable controlling its gradation. The proposed technique defined the cluster dotes of AM to set at the center that surrounded by dispersed dots of FM. The experiment suggests that, to achieve good hybrid screen printing, the boundary cutoff at 180-220 code value; with dpi/lpi ratio at over 12. In addition, the range of bandwidth of screen mixing area should be 10-30 code value where by FM screen falls in the highlight area category.