Abstract: In order to improve the clarity of haze images,this paper proposes a haze removal algorithm combining the fractional differential,the dark channel prior and the Retinex.In the algorithm,a high-texture haze image is processed first through the fractional differential and then through the dark channel prior.Moreover,on the basis of the depth map obtained through the dark channel prior,the Retinex scales are calculated in each part of the processed image.Finally,the image enhancement result is got by performing the Retinex transform of the image after the fractional differential operation.The test results of a number of haze images show that the new algorithm can effectively improve the clarity of haze images with less Retinex halo phenomena,and in comparison with the existing dark channel prior and multi-scale Retinex algorithms,it has a higher processing speed and a better image enhancement effect for the haze images of the high texture and great scene depth difference.

Key words: image enhancement, haze, fractional differential, dark channel prior, Retinex transform, multi-scale variation