Reversible data hiding (RDH) with contrast enhancement (RDH-CE) is a special type of RDH in improving the subjective visual perception by enhancing the image contrast during the process of data embedding. In RDH-CE, data hiding is achieved via pairwise histogram expansion, and the embedding rate can be increased by performing multiple cycles of histogram expansions. However, when embedding rate gets high, human visible image degradation is observed. Previous work designed an upper bound of the embedding level for RDH-CE, which effectively avoids image over-sharping but offers limited embedding capacity. In this paper, a better tunable bound is designed to enhance the embedding capacity of RDH-CE by exploiting the characteristics of histogram distribution. Furthermore, the objective distortion introduced by histogram pre-shifting is minimized when the embedding level is no more than the upper bound, and the human visible degradation is minimized when the embedding level exceeds the limitation of the proposed upper bound. Experimental results validate that the proposed method provides appropriate upper bound of the embedding level, increases the effective embedding capacity and offers better image contrast.

中文翻译：

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通过对比增强可逆数据隐藏的性能

具有对比度增强功能的可逆数据隐藏（RDH）（RDH-CE）是RDH的一种特殊类型，它通过在数据嵌入过程中增强图像对比度来改善主观视觉。在RDH-CE中，可通过成对的直方图扩展来实现数据隐藏，并且可以通过执行多个周期的直方图扩展来提高嵌入率。然而，当嵌入率变高时，观察到人的可见图像劣化。先前的工作为RDH-CE设计了嵌入级别的上限，这可以有效避免图像过分锐利，但嵌入能力有限。本文利用直方图分布的特点设计了一个更好的可调边界，以提高RDH-CE的嵌入能力。此外，当嵌入水平不超过上限时，由直方图预移引入的客观失真最小，而当嵌入水平超过建议的上限时，则人类可见的劣化最小。实验结果证明，该方法可以提供适当的嵌入水平上限，提高有效嵌入量，并提供更好的图像对比度。