Illumination-invariant representation for natural color images and its application

Illumination factors such as shading, shadow, and specular highlight, observed from object surfaces in a natural scene, affect seriously the appearance and analysis of the color images. This paper proposes an illumination-invariant representation that is derived from the standard dichromatic reflection model for inhomogeneous dielectric and the extended dichromatic reflection model for homogeneous metal. Illumination color is estimated from specular reflection component on inhomogeneous surfaces without using a reference white standard. The overall performance of the proposed representation is examined in experiments using real-world objects including metals and dielectrics in detail. The feasibility of effective edge detection is introduced and compared with the state-of-the-art illumination-invariant methods.