Histogram Equalization Utilizing Spatial Correlation For Image Enhancement
Mohamed S. Kamel, Lian Guan · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1989
Histogram equalization (HE) techniques are widely used for image enhancement due to their simplicity and effectiveness. Most of the existing HE techniques assume image pixels to be randomly distributed over the image space. In general, adjacent image pixels are highly correlated, it is more reasonable to design HE methods that utilize this correlation. In this paper, we present a method of HE that takes spatial correlation among pixels into account. The concurrence of the gray values of adjacent pixels is calculated to form conditional probabilities of each gray level with respect to other gray levels in the image. The HE is then obtained using these probabilities. We call this method Conditional Histogram Equalization (CHE). Experimental results show that the proposed method generates images that are visually more pleasant than the ones generated by conventional HE techniques. The results also show that this method avoids the problem of over stretching the contrast in images with highly peaked histograms.