Objective Colour from Multispectral Imaging

The light reflected from a surface depends on the scene geometry, the incident illumination and the surface material. One of the properties of the material is its albedo ρ(λ) and its variation with respect to wavelength. The albedo of a surface is purely a physical property. Our perception of albedo is commonly referred to as colour. This paper presents a novel methodology for extracting the albedo of the various materials in the scene independent of incident light and scene geometry. A scene is captured under different narrow-band colour filters and the spectral derivatives of the scene are computed. The resulting spectral derivatives form a spectral gradient at each pixel. This spectral gradient is a normalized albedo descriptor which is invariant to scene geometry and incident illumination for diffuse surfaces.