An adaptive image enhancement algorithm based on discrete cosine transform
Wei Li · Engineering Journal of Wuhan University · 2009
An adaptive image enhancement algorithm in the spectral domain is proposed.The image is translated to the spectral domain with the discrete cosine transform(DCT) algorithm.According to the corresponding relations between the spatial image and the spectral coefficient,the α-rooting algorithm is used to adjust the low frequency coefficients,which compresses image dynamics and enhances image details in the bright or dark regions.The high frequency coefficients are divided into the four parts.Every part coefficient is adjusted with multi-scale nonlinear operator based on human visual perception,which enhances the big bulk edge details,restrains the feeble noise and improves the image contrast.Moreover using the energy distribution of the DCT coefficients which is defined directly in each DCT block of an image to confirm the controlled parameter of low frequency coefficients,which is effective to eliminate the block artifacts.The experimental results show that the enhanced image is sharp and distinct,which has an obvious improvement about visual effect.