Center for Soft Computing Research, Indian Statistical Institute, Kolkata, 700108 India.
IEEE Trans Image Process. 2011 May;20(5):1211-20. doi: 10.1109/TIP.2010.2083676. Epub 2010 Oct 4.
Histogram equalization, which aims at information maximization, is widely used in different ways to perform contrast enhancement in images. In this paper, an automatic exact histogram specification technique is proposed and used for global and local contrast enhancement of images. The desired histogram is obtained by first subjecting the image histogram to a modification process and then by maximizing a measure that represents increase in information and decrease in ambiguity. A new method of measuring image contrast based upon local band-limited approach and center-surround retinal receptive field model is also devised in this paper. This method works at multiple scales (frequency bands) and combines the contrast measures obtained at different scales using L(p)-norm. In comparison to a few existing methods, the effectiveness of the proposed automatic exact histogram specification technique in enhancing contrasts of images is demonstrated through qualitative analysis and the proposed image contrast measure based quantitative analysis.
直方图均衡化旨在实现信息最大化，被广泛应用于以不同方式对图像进行对比度增强。本文提出了一种自动精确直方图规范技术，并将其用于图像的全局和局部对比度增强。通过首先对图像直方图进行修改处理，然后最大化表示信息增加和模糊度降低的度量，获得所需的直方图。本文还设计了一种基于局部带限方法和中心-环绕视网膜感受野模型的新的图像对比度测量方法。该方法在多个尺度（频带）上工作，并使用 L(p)-范数组合在不同尺度上获得的对比度度量。与现有的几种方法相比，通过定性分析和基于所提出的图像对比度度量的定量分析，证明了所提出的自动精确直方图规范技术在增强图像对比度方面的有效性。
