Color Reproduction of Facial Pattern and Endoscopic Image Based on Color Appearance Models

Declaration This is to certify that this work has been done by me and it has not been submitted elsewhere for the award of any degree or diploma. Abstract In recent years, many imaging systems have been developed, and it became increasingly important to exchange image data through the computer network. Therefore, it is required to reproduce color independently on each imaging device. In the studies of device independent color reproduction, colorimetric color reproduction has been done, namely color with same chromaticity or tristimulus values is reproduced. However, even if the tristimulus values are the same, color appearance is not always same under different viewing conditions. Therefore we must introduce color appearance prediction for color reproduction of image. In this dissertation, a new color reproduction method based on color appearance prediction is introduced for color reproduction of facial pattern and endoscopic image. First, spectral reflectance of skin color was analyzed by principal component analysis, and it was shown that the spectral reflectance of skin can be estimated by three principal components. On the basis of these experimental results, spectral reflectances of facial pattern taken by HDTV camera was estimated, and computer simulation of colorimetric color reproduction has been done using those obtained spectral reflectances. Color appearance models of von Kries, Fairchild, LAB were also introduced to this color reproduction algorithm. The image calculated by those models were compared with the color hardcopies under various illuminants (" A " , " Day Light " , " Horizon " , and " Cool White ") using memory matching technique. It was found that the Fairchild model is most significant to estimate the color appearance of skin color chart under different illuminants. However, the model was not significant to apply to estimation of color appearance in facial pattern. Therefore, modified Fairchild model was introduced to estimate the color appearance of facial pattern. It was shown in psychophysical experiments that the model can estimate well the color appearance of facial pattern compared to other models. vii These experiments have been done in the dark environment. However, the practical image on a CRT is usually watched under the environmental illuminant. We must apply color appearance models to reproduce image on a CRT under various illuminants, specially for remote diagnosis of endoscopic images. It is necessary to do a gamut-mapping for image which cannot be reproduced in gamut of CRT. However, up to this time, there …