Improved methods of estimating shape from shading using the light source coordinate system

摘要

This paper develops improved methods of estimating local surface orientation from shading information with the aid of a coordinate system having one axis in the (assumed) direction of the light source. In this system, the surface tilt is related to the direction of the gray level gradient at the given point. An alternative formulation of the surface slant probability density is developed that takes the discrete nature of digital images into account, and that yields a better estimate of the light source direction.