Shadow detection via Rayleigh scattering and Mie theory

Abstract

In this paper, we present a method to detect shadows in outdoor scenes. Here, we note that the shadow areas correspond to the diffuse skylight which arises from the scattering of the sunlight by particles in the atmosphere. This yields a treatment in which shadows in the image can be viewed as a linear combination of scattered light obeying Rayleigh scattering and Mie theory. This treatment allows for the computation of a ratio which permits casting the problem of recovering the shadowed areas in the image into a clustering setting making use of active contours. We illustrate the utility of the method for purposes of detecting shadows in real-world imagery and compare our results against a number of alternatives elsewhere in the literature.