Applying Color Appearance Model CAM16‐UCS in Image Processing Under HDR Viewing Conditions

ABSTRACT Achieving successful cross‐media color reproduction is very important in image processing. The purpose of this study is to accumulate high dynamic range data to verify and modify the CAM16‐UCS model. There are two experiments in this study. The first experiment was aimed to collect corresponding data of color patches between colors on a display and the real scene viewed under high dynamic range viewing conditions. The results were used to refine CAM16‐UCS model. Six illumination levels (i.e., 15, 100, 1000, 3160, 10 000, and 32 000 lx) and 13 test color samples were used in the experiment. Ten observers adjusted the color patches on the display to match the color samples of the real scene. The visual results showed a clear trend, an increase in the illumination level raised vividness perception (both increase in lightness and colorfulness). However, CAM16‐UCS did not give accurate prediction to the visual results, especially in the lightness direction. The model was then refined to achieve satisfactory performance and to truthfully reflect the visual phenomena. However, the effect of the modified model could not achieve successful color image reproduction, especially under low illumination conditions. Experiment 2 was conducted by adjusting the overall lightness and colorfulness of the image. The results were used to extend the model for image reproduction. Also, an independent experiment verified that the image generated by the new model matched the real environment well, indicating that the model can perform well in scene restoration.