Images captured in foggy weather are of ten degraded byatmospheric absorption and scattering.Haze removal is highly desired in image processing and computer vision applications. Removing haze can significantly increase the visibility of the scene. In addition

most image processing and computer vision algorithms usually assume that the input image is the scene radiance. Therefore

several methods for haze removal have been proposed.However

the sky region processed by most of these algorithms is degraded by block noise and serious color distortion. To address this issue

this paper proposes an improved single image haze removal method based on sky region detection and dark channel prior. Our proposed method consists of three major stages: sky region detection

haze removal

and tone mapping. In the first stage

sky is usually a large and smooth region with high intensity. On the basis of these characteristics

an effective algorithm is designed to divide the input image into “sky” and “non-sky”regions. In the next stage

dark channel prior is used to estimate the transmission maps of the two regions

and a guided filter is applied to refine these maps

such that the haze-free image can be recovered by the atmosphere scattering model. The final stage uses a simple tone mapping algorithm to increase the image brightness

which leads to good visual effects. In He's haze removal algorithm

dark channel prior is no longer a good prior because sky regions may have high intensity.Consequently

the sky region of the recovered haze-free image will have serious noise and color distortion. We combine sky region detection and dark channel prior to eliminate noise and color distortion. Several experiments show that images restored by the proposed algorithm are clear and natural. In particular

the sky region is smooth and bright. Dark channel prior is a very good prior for image haze removal

but it is not suitable for sky regions because it leads to block noise and serious color distortion. On the basis of sky region detection

a novel single image haze removal algorithm is proposed in this paper. The presented algorithm can achieve better results than the defogging algorithms proposed by He Kaiming and Tarel.