Non-uniform illumination endoscopic imaging enhancement via anti-degraded model and L 1 L 2 -based variational retinex. - Rao, Zhitao; Xu, Tingfa; Luo, Jiqiang; Guo, Jie; Shi, Guokai; Wang, Hongqing (EURASIP J. Wirel. Commun. Netw., 2017)