Yuri MURAKAMI^1,3, Hiroyuki MANABE², Takashi OBI^2,3, Masahiro YAMAGUCHI^2,3 and Nagaaki OHYAMA^1,3

¹Frontier Collaborative Research Center, Tokyo Institute of Technology, 4259 Nagatsuda-cho, Midori-ku, Yokohama 226-8503, Japan
²Imaging Science & Engineering Laboratory, Tokyo Institute of Technology, 4259 Nagatsuda-cho, Midori-ku, Yokohama 226-8503, Japan
³Telecommunications Advancement Organization of Japan, Akasaka Natural Vision Research Center, 2-17-28, Akasaka, Minato-ku, Tokyo 107-0052, Japan

(Received September 29, 2003; Accepted January 16, 2004; Revised December 25, 2003)

Recently, multispectral images have been utilized for high fidelity color reproduction through visual tele-communication systems and its compression schemes have been required. However multispectral image coding considering color degradation has not been established. This article presents a comparison of four spectral transforms presented before to find out which transform is more suitable to a spectral decorrelation scheme in transform coding of multispectral images. Transforms dealt with in this paper are Karhunen-Loeve transform (KLT), weighted KLT (WKLT), one mode analysis (OMA) and a transform realizing compatibility to the conventional color systems, latter three of which are designed to represent spectral reflectance functions with small number of coefficients having small colorimetric errors. Through the theoretical and experimental comparisons, it is found that WKLT and OMA reduced colorimetric error compared to the others, where OMA is suitable when the rendering illuminations in the color reproduction can be assumed in advance and WKLT is applicable to other situations.

Key words: multispectral image, transform coding, spectral transform, color reproduction, KLT, decorrelation