Image Enhancement Algorithm Combines Maximum Gray Frequency Restrict with Dynamic Histogram Equalization
基于极大灰度频数抑制结合动态直方图均衡的图像增强算法

General histogram equalization technology have two drawbacks, it makes the enhanced image have a higher contrast while improvement of contrast dependents on heavily the distribution of gray frequency. So it often leads to enhance high frequency gray level excessively while compresses low frequency gray level. In addition, the enhance process lacks purpose, so it is difficult to meet the special requirements such as to enhance the specified interesting gray level. In order to solve this problem, image enhancement algorithm combines maximum gray frequency restrict with dynamic histogram equalization is proposed in this paper. Firstly, according to analyzing the image histogram and the interested in gray range, the gray range of each sub-level mapping and the frequency control threshold are selected. Then histograms of sub-level after restricting the maximum gray frequency are redefined, by adopting histogram equalization algorithm to construct gray transfer function, mapping sub-level gray to the appointed range. Finally the enhancement result of sub-level is composed. The experimental results demonstrate that this image enhancement algorithm not only could change the situation of the excessive enhancement, but also could control the interest gray level range, and it solves the application requirement that the image contrast enhancement could be controlled.