NIUIE: Nonuniform Illumination Underwater Image Enhancement via Illumination Component Estimation

Artificial lighting has become a common auxiliary equipment for underwater visual tasks. It effectively extends visibility into regions where natural light is insufficient or entirely absent, but it also inevitably introduces non-uniform illumination. In underwater environments, visual perception is inherently affected by scattering-induced haze and by wavelength-dependent attenuation, which result in color distortion. The interaction between non-uniform artificial illumination and these inherent degradations further exacerbates the complexity of underwater image formation, thereby significantly increasing the difficulty of underwater image enhancement. However, most existing underwater image enhancement methods fail to explicitly account for this coupling effect. To this end, we propose a novel illumination component for Retinex model, consisting of two parts: the Color Part and Light Part. Based on the new illumination component, we further introduce a non-uniform illumination underwater image enhancement method (NIUIE). Firstly, an illumination correction method is proposed to obtain the Light Part by combining the gamma correction with dual illumination maps. Then, the Color Part is derived from a color correct method based on nonlinear channel compensation. Finally, the initial illumination component is optimized with a weighted regularization term which is efficiently solved using the alternating direction method of multipliers (ADMM). Comprehensive comparisons on five challenging underwater datasets demonstrate that NIUIE outperforms several state-of-the-art underwater image enhancement algorithms qualitatively and quantitatively. Furthermore, the effectiveness of NIUIE is also validated on other visual tasks, including non-uniform illumination enhancement for aerial images and feature matching in underwater images. Experimental results show that the proposed method effectively addresses the problem of non-uniform illumination and common underwater issues simultaneously, improving details in both high-light and low-light regions.