Adaptive Sigmoid Function to Enhance Low Contrast Images

Image enhancement is one of the most important issues in lowlevel image processing. Mainly, enhancement methods can be classified into two classes: global and local methods. Various enhancement schemes are used for enhancing an image which includes gray scale manipulation, filtering and Histogram Equalization (HE).Histogram Equalization (HE) has proved to be a simple and effective image contrast enhancement technique. In this paper, the global histogram equalization is improved by using sigmoid function combined with local enhancement statistics. Experimental results demonstrate that the proposed method can enhance the images effectively. The performances of the existing techniques and the proposed method are evaluated in terms of SNR, PSNR, CoC. Keywordscontrast enhancement, sigmoid function, Histogram Equalization, image processing

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