Color and gloss reproduction from multispectral images

Abstract

We propose a new technique to reproduce faithfully both the color and the gloss of an object on a computer, using multispectral images. An imaging spectrograph equipped with a monochrome charge-coupled device (CCD) camera is fixed in front of the target object. Multispectral images of a linear portion of the object's surface are captured at suitable intervals by a measuring system which comprises a light source orbiting the target object. To obtain spectral images for the whole surface, the target object is also rotated. The reflection is separated into diffuse and specular components, according to the dichromatic reflection model, and the diffuse parameters are estimated at 5-nm intervals between 380nm and 780nm for each pixel. Since the CCD camera used to capture images has a limited dynamic range, we suppose that the specular reflection is independent of wavelength for the dielectrics, and that the specular reflections are saturated, although some of them can be non-saturated. We adopt the Torrance-Sparrow reflectance model for the specular reflection, and estimate the specular parameters using the least squares method for each pixel. Our experimental results reveal that the diffuse parameters for the color and the specular parameters for the gloss of the target object are satisfactorily estimated.