Color in perspective

Simple constraints on the sets of possible surface reflectance and illuminants are exploited in a new color constancy algorithm that builds upon Forsyth´s (1990) theory of color constancy. Forsyth´s method invokes the constraint that the surface colors under a canonical illuminant all fall within an established maximal convex gamut of possible colors. However, the method works only when restrictive conditions are imposed on the world: the illumination must be uniform, the surfaces must be planar, and there can be no specularities. To overcome these restrictions, we modify Forsyth´s algorithm so that it works with the colors under a perspective projection (in a chromaticity space). The new algorithm working in perspective is simpler than Forsyth´s method and more importantly the restrictions on the illuminant, surface shape and specularities can be relaxed. The algorithm is then extended to include a maximal gamut constraint on a set of illuminants that is analogous to the gamut constraint on surface colors. Tests on real images show that the algorithm provides good color constancy