Color Correction Scheme for Tongue Images

Color images produced by digital cameras are usually device-dependent, i.e., the generated color information (usually presented in the RGB color space) is dependent on the imaging characteristics of specific cameras. This is a serious problem in computer-aided tongue image analysis because it relies on the accurate rendering of color information. In this chapter, we propose an optimized correction scheme that corrects tongue images captured in different device-dependent color spaces to the target device-independent color space. The correction algorithm in this scheme is generated by comparing several popular correction algorithms, i.e., polynomial-based regression, ridge regression, support-vector regression, and neural network mapping algorithms. We tested the performance of the proposed scheme by computing the CIE L * a * b * color difference (∆E ab * ) between estimated values and the target reference values. The experimental results on the colorchecker show that the color difference is less than 5 (∆E ab * < 5), while the experimental results on real tongue images show that the distorted tongue images (captured in various device-dependent color spaces) become more consistent with each other. In fact, the average color difference among them is greatly reduced by more than 95%.