IEEE Trans Image Process. 2016 Jul;25(7):2971-2982. doi: 10.1109/TIP.2016.2552723.
Digital multitoning is an extension of halftoning for rendering more than two tones at each pixel for higher image quality. Although a lot of effort has been put in generating dispersed dots previously, the blue-noise feature can hardly be achieved for those printers utilizing the electrophotography (EP) process to avoid the physically unstable isolated dots. To overcome this issue, Chandu et al. proposed a screening method for yielding green-noise dot clusters, yet noisy multitone texture was accompanied. This degrades the visual quality and the stability of tone rendering. In this paper, a significantly improved homogeneity of clustered dots can be achieved by the proposed screening method based upon the new inter-iterative clustered-dot direct multi-bit search algorithm. Compared with the former approaches, the inter-iteration design leads to less error by the updated initial multitone patterns. As demonstrated in the experimental results, both of the high homogenous multitone texture and less noisy perception at all absorptance levels are offered in contrast to the former Chandu et al.'s results. The high-quality output proves it as a very competitive candidate for EP printers, e.g., laser printers.
数字调谐是半色调的扩展，用于在每个像素上呈现两种以上的色调，以提高图像质量。尽管之前已经做了很多努力来生成分散的点，但对于那些利用静电印刷（EP）工艺的打印机来说，由于要避免物理上不稳定的孤立点，很难实现蓝噪声特征。为了克服这个问题，Chandu 等人提出了一种用于生成绿噪声点簇的筛选方法，但随之产生了噪声多色调纹理。这会降低视觉质量和色调渲染的稳定性。在本文中，通过基于新的迭代间聚类点直接多位搜索算法的改进筛选方法，可以实现聚类点的显著提高均匀性。与以前的方法相比，通过更新的初始多色调模式，迭代间设计会导致更少的误差。如实验结果所示，与 Chandu 等人之前的结果相比，在所有吸收率水平下，均提供了具有更高同质性的多色调纹理和更少的噪声感知。高质量的输出证明它是 EP 打印机（例如激光打印机）的一个极具竞争力的候选方案。
