18 January 2010 Memory efficient hierarchical error diffusion
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Hierarchical Error Diffusion (HED) developed in [14] yields high-quality color halftone by explicitly designing three critical factors: dot overlapping, positioning, and coloring. However, HED requires more error memory buffer than the conventional error diffusion algorithms since the pixel error is diffused in dot-color domain, instead of colorant domain. This can potentially be an issue for certain low-cost hardware implementation. This paper develops a memory-efficient HED algorithm (MEHED). To achieve this goal, the pixel error in dot-color domain is converted backward and diffused to future pixels in input colorant domain, say, CMYK for print applications. Since the error-augmented pixel value is no longer bounded within the range [0, 1.0], the dot overlapping control algorithm developed in [14] needs to be generalized to coherently handle the pixel density of outside the normal range. The key is to carefully split the modified pixel density into three parts: negative, regular, and surplus densities. The determination of regular and surplus densities needs to be dependent on the density of K channel, in order to maintain local color and avoid halftone texture artifact. The resulting dot-color densities are serves as the input to hierarchical thresholding and coloring steps to generate final halftone output. Experimental results demonstrate that MEHED achieves similar image quality compared to HED.
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Zhen He, Zhen He, Zhigang Fan, Zhigang Fan, } "Memory efficient hierarchical error diffusion", Proc. SPIE 7528, Color Imaging XV: Displaying, Processing, Hardcopy, and Applications, 75280X (18 January 2010); doi: 10.1117/12.836032; https://doi.org/10.1117/12.836032

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