Wavelet domain Retinex algorithm for image contrast enhancement

Multiscale Retinex with Color Restoration (MSRCR) algorithm has an extensive usage in many different applications and performs well for a very large variety of natural images. However, processing in three spectral channels for at least three distinct scale constants makes the algorithm time consuming. In addition, optimal performance is not always obtained with default parameter settings, especially when images that have a dark subject with a very bright background are being processed. In this paper, to overcome the drawbacks of the Retinex algorithm, a wavelet transform (WT) based Retinex approach is proposed, in which a modified version of the MSRCR algorithm is applied to the approximation coefficients of the transformed image. The detail coefficients are also changed in order to provide sharpness besides contrast enhancement. The proposed algorithm has less computational complexity, and also provides more realistic rendition compared to MSRCR.