Contrast Enhancement Evaluation Database (CEED2016)

The CEED2016 is newly developed image database dedicated to contrast enhancement evaluation. The database contains 30 original color images and 180 enhanced images obtained using six different CE methods. The database is built with our own captured images and some common pictures used by the image processing community. The subjective experiments were performed at Universite Paris 13, Sorbonne Paris Cité at Laboratoire de Traitement et Transport de l’Information (L2TI). The images were displayed on a calibrated LCD monitor in a dark room environment to avoid any problem with the illumination adaptation of background. Twenty-three observers, 10 experts, and 13 non-experts, from different age groups, gender, and background participated in the experiments. To obtain the ranking scores, we adopted a balanced pairwise preference based ranking protocol. The interface for the subjective experiments was developed in Matlab, where, for each original image, we randomly displayed all possible pair combinations of enhanced images to the observers. We also showed the original image in the center of the screen (a pair of enhanced images are displayed to its left and right), to facilitate the analysis of after effects of CE. The observers had the choice to rank equally similar stimuli. In the PC ranking protocol, each enhanced image is compared with the others in pairs and ranking results are stored in a preference matrix.