Color from black-and-white surveillance cameras

In criminal investigation, the color of the clothes that a suspect wore is very important information. When the suspect was imaged by a color surveillance camera, this information is available. However, if the camera was black-and-white, it is usually impossible to obtain this information. Nevertheless, if the suspect was imaged under several different illuminations, some color information can be estimated depending on the variation of the illuminations, even if the images themselves are black-and-white. In this paper, we formulate this problem, and on the basis of the formulation, we discuss what kind of color information can be obtained under given illumination conditions. Experimental results are shown to demonstrate the effectiveness of the method. Apart from criminal investigation, if we actively control the illumination, the method can be used as a method for measuring spectral reflectance. This subject is also discussed.