Pre-processing for single image dehazing

Existing single image haze removal algorithms could suffer from noise amplification in sky regions and possible color distortion in restored images due to noise in haze images. In this paper, a simple pre-processing tool is introduced for single image haze removal so as to reduce the effect of noise in the restored image. The input image is first decomposed into base and detail layers by using a weighted guided image filter (WGIF). The airlight and transmission map are estimated from the base layer. In order to restore the objects close to the camera well, the decomposition of haze image is adaptive to the value of the transmission map. If the transmission map of a pixel is small, it is decomposed into two layers, otherwise, not decomposed. Since the noise is included in the detail layer, the base layer is amplified in the final image if the haze image is decomposed. Experiments show that the proposed pre-processing tool can indeed be applied to improve the state-of-the-art haze removal algorithms.