关键词: 对比度增强, 直方图均衡化, 直方图规定化, 变分法, 保持熵值

Abstract: Histogram Equalization（HE） is a simple and effective contrast enhancing technique, but it can’t preserve the mean brightness and the entropy of the image, and hence is seldom suitable for actual application. This paper proposes a new method about histogram specification to overcome those drawbacks of HE. This method（EPHEMP） makes the histogram as flat as possible by the fundamental idea of HE, and by the variation algorithm, finds a suitable target histogram maximize the mean brightness under the constraint that the entropy is constant, at last transforms the original histogram to that target one by histogram specification. Comparing to the existing methods including HE, BBHE, DSIHE, MMBEBHE, and BPHEME, experimental results show that EPHEMP can not only preserve the entropy, but also enhance the contrast of the image effectively. And hence it is possible to be used for many commercial purposes such as consumer electronic products.

Key words: contrast enhancement, histogram equalization, histogram specification, variation approach, entropy preserving