It is critical to restore and preserve edge details in image defogging. In existing classical model-based defogging methods

medium transmittance is computed directly

i.e.

image matting refinement follows transmittance estimation

so the computational complexity is high. In order to reduce time complexity

transmittance is indirectly computed in virtue of bilateral filtering. In the solution of medium transmittance based on bilateral filtering

atmospheric scattering function and light value are relatively accurately estimated; therefore

transmittance can be indirectly computed. The proposed algorithm avoids the image software matting for medium transmittance refinement

so real-time performance is improved. The experiments are performed on two sets of outdoor foggy image to compare transmittance map

restoration effect

and operation time. In the proposed method

transmission distribution map is clearer

and the block effect of transmittance estimation is restricted. Image edges are smoothed during transmittance refinement. The operation time of the proposed algorithm is just 1.803 second for the image with the size of 608×456. In the global enhancement of foggy image of this paper

the local details are restored and the edges are preserved. Consequently

the proposed algorithm is suitable for image detection systems. The experiment results show that the proposed algorithm can protect edge details besides improving time efficiency.