Natural Vision Image Data File Format for Spectral-Based Color Reproduction

Natural Vision Image Data File Format has been developed in order to realize spectral-based color reproduction. This paper introduces the profile format of Natural Vision Image Data File Format. It is based on ICC Profile Format. New Profiles, Tags and Tag Types, therefore, have been developed to cover the lacks of ICC Profile Format for spectral-based color reproduction. The design concepts of Natural Vision System are introduced with respect to the requirements. Input Profiles and Display Profiles are expanded in order to provide spectral characteristics to color reproduction system. ColorSpace Conversion Profiles is expanded in order to provide rendering illuminant and CMFs to Color Reproduction Intent Management System. Relationships between the expanded Profiles and image processing are also descried. Introduction Spectral-based color reproduction system has more flexibility and reliability rather than colorimetric-based one from the viewpoint of colorimetry. The establishment of CIE Technical Committee 8-07 multispectral imaging symbolizes the importance of spectral-based color reproduction. Ohsawa has summarized the concept of spectralbased color reproduction system. The basic architecture of Natural Vision Image Data File Format also has been introduced as the solution of spectral-based color reproduction system. This paper introduces the details of the profile component. Relationship between the profile format and image processing is also explained. Design Concepts of Natural Vision System The following three requirements are established for the design of Natural Vision system: 1) To handle spectral data (R-1) 2) To be acceptable arbitrary illuminants (R-2) 3) To be acceptable arbitrary Color Matching Functions (CMFs) (R-3) 4) To be compatible with current system (R-4) Color reproduction system that realizes the above requirements has the following benefits: a) R-1 overcomes the problems of metameric matching. b) R-2 makes possible illumination exchanges. c) R-3 makes possible optimizations for individual CMFs. d) R-4 gives flexibility to Natural Vision System. Based on the above idea, Natural Vision system is designed as shown in Fig.1. To satisfy R-1, capturing system has to provide spectral reflectance or radiance of the object. Color Reproduction Intent Management System (CRI management system) is in charge of determining color reproduction target. To satisfy R-2 and R-3, CRI Management System has to be acceptable arbitrary illuminants (i.e. Etarget) and CMFs (i.e. ctarget) given by ColorSpace Conversion Profiles. In other words, color reproduction target (i.e. Sestimated,target or Cestimated,target) has to be able to define with the arbitrary illuminants and CMFs. The number of dimension of stimulus value C should be arbitrary. To satisfy R-4, the profile format is based on ICC profile format, AVI or BMP is used as the image format, and WAV format is used as the audio format in Natural Vision Image Data File Format. Figure 2 illustrates the details of the capturing system. It consists of multi-band camera, spectral estimation module and colorimetric estimation module. Input Profiles has to provide spectral characteristics of multi-band camera. The multi-band structure is useful to heighten the accuracy of the spectral estimation. Figure 3 illustrates the details of the CRI management system. It consists of spectral targeting module, colorimetric targeting module. The spectral targeting module is able to accept arbitrary illuminations (i.e. Etarget). The colorimetric targeting module is also able to accept arbitrary CMFs (i.e. ctarget). * The term “stimulus value” corresponds generalized (i.e. multidimensional) XYZ. Tristimulus value is a part of the stimulus value, where the number of dimension is three. ** The term “multi-band” means that the number of bands is arbitrary. Three-band camera (i.e. RGB camera) is included to the multi-band camera. It does not restrict that the number of the bands is over three. IS&T's 2003 PICS Conference