Low-light Image Enhancement Method by Soft-closing Using Local Histogram

Recently, various low-light image enhancement methods are proposed. LIME is one of the low-light image enhancement methods based on Retinex theory. Retinex theory assumes that the image is decomposed into the illumination component and the reflectance component. In LIME, the illumination map is estimated by solving optimization problem for edge-aware smoothing and the output image is obtained by adjusting the illumination map. Though LIME significantly enhances the contrast in dark regions, it tends to cause clipping in the bright regions. In this paper, we propose a new method of low-light image enhancement. In the proposed method, firstly the illumination map is estimated by the soft-closing operation using smoothed local histogram. Then, the output image is obtained by adjusting the illumination in the same way as LIME. The proposed method can improve the contrast of the image overall while suppressing clipping in bright regions. The effectiveness of the proposed method is verified by experiments using various images.