Fig. 1. Diagram of filtering characteristics in different types of support regions

Fig. 2. Center pixel located in position of eight sub windows

Fig. 3. Sub-window box filter under different parameter conditions

Fig. 4. Flow chart of sub-window box filter operation

Fig. 5. Performance comparison in edge preserving between guided filter and proposed filter

Fig. 6. Flow chart of proposed low-level-light image enhancement algorithm

Fig. 7. Histogram distribution of low-level-light image before and after algorithm processing

Fig. 8. Cumulative histogram probability distribution

Fig. 9. Effect comparison of histogram equalization in different scenes

Fig. 10. Detail layer enhancement of low-level-light image

Fig. 11. Physical drawing of experimental platform

Fig. 12. Internal structure of experimental platform

Fig. 13. Raw images obtained at different levels of illumination

Fig. 14. Comparison of effect of image enhancement by algorithms under${10}^{-1}\text{lx}$ low-level-light condition

Fig. 15. Comparison of effect of image enhancement by algorithms under${10}^{-3}\text{lx}$ low-level-light condition

Fig. 16. Comparison of effect of image enhancement by algorithms under${10}^{-5}\text{lx}$ low-level-light condition