Image contrast enhancement by preserving brightness using global and local features

Image enhancement is one of the most significant techniques in digital image processing. This paper introduces two image enhancement methods, Weighted of Local and Bidirectional Smooth Histogram Stretching (WLBSHS) and Local then Bidirectional Smooth Histogram Stretching (LBSHS). WLBSHS uses local and global enhancement in weighted approach. Main purpose of local enhancement is sharpening edges of objective and exploring local information. For global enhancement, Bidirectional Smooth Histogram Stretching (BSHS) method is used. We divide the histogram in two parts and use forward and backward gamma transform on these parts, with bin interval control mechanism. We develop the hybrid method which is use to enhance the contrast of image with preserving its brightness by making the mixture of global and local enhancement. In this research we considered AMBE, E, PSNR EME, BR parameters for evaluating the enhanced image. This hybrid method is found to be better than AWIE, AGCID and VHA.