High-speed quantile-based histogram equalisation for brightness preservation and contrast enhancement

In this study, the authors introduce a new histogram equalisation-based contrast enhancement method called high-speed quantile-based histogram equalisation (HSQHE) suitable for high contrast digital images. The proposed method is an effective tool to deal with the `mean-shift´ problem, which is a usual problem with the histogram equalisation-based contrast enhancement methods. The main idea of HSQHE is to divide input image histogram into two or more sub-histograms, where segmentation is based on quantile values. Since the histogram segmentation is based on the quantile values, the entire spectrum of grey level will always play an important role in enhancement process. In addition, the proposed method does not require the recursive segmentation of the histogram as in many other methods, and hence the proposed method requires less time for segmentation. The experimental results show that the performance of the proposed HSQHE method is better as compared with other existing methods available in the literature. In addition, this method preserves image brightness more accurately than the prevailing state of art and takes less time as compared with the other methods.