A new Retinex algorithm based on variable filters is proposed to improve the existing center-surround Retinex algorithm.The proposed algorithm can enhance details effectively while maintaining the color fidelity in the applications of foggy images enhancement.The existing center-surround Retinex algorithm cannot achieve such function because of the utilizing of fixed filter.First the thresholds are worked out according to the image quality distributing.Then in each sub-block,the algorithm uses the local inf...