Single underwater image restoration using attenuation-curve prior

Underwater images suffer from low contrast and color distortion due to the existence of dust-like particles and light attenuation. Some previous works using the patch-based priors, e.g. adaptations of the dark channel prior, cannot achieve satisfactory results in both contrast enhancement and color restoration in the underwater environment. In this paper, we propose a novel underwater image restoration method based on a non-local prior, termed an attenuation-curve prior. This prior relies on the observation that colors of a clear image can be well approximated by several hundred distinct color clusters and the pixels in the same color cluster will form a power function curved line in RGB space after their colors are attenuated by water. Our work mainly contains two steps. Firstly, we estimate the waterlight based on its smoothness properties and the different attenuation coefficient of light. Secondly, we estimate the transmission map using the attenuation-curve prior. Once the waterlight and transmission are obtained, the clear underwater image can be restored. Experimental results demonstrate that our proposed method can achieve better results when comparing with state-of-the-art approaches.