Abstract: Aiming at the problem of the complexity of dark channel prior fog removal algorithm, and using guided filtering to refine the atmospheric transmittance layer for a long time, we proposed an algorithm to refine transmittance layer by the median filtering to improve the fog removal spe
ed of aerial image. The improved algorithm defined a simple median filter with edge protection effect, independent of the filtering window and time complexity of O(1).  The blocky processing result generated by calculating the dark channel layer was better blurred by the median filter for the uniform cloud input image. The effect of fog removal image before and after improvement of the algorithm was compared by computer encoding and objective image quality assessment method without reference. The quantitative analysis and experimental results show that the median filtering algorithm is easier to implement than the guided filtering when the original image is evenly distributed. It can not only save fog removal time, but also realize image smoothing.

Key words: aerial image, dark channel prior, fog removal algorithm, filtering, processing speed