Shape from shading for multiple albedo images

Most shape from shading (SFS) algorithms assume that objects in the scene are Lambertian reflectors, i.e., they do not absorb any radiation for any wavelength. However, real objects reflect only part of the incoming radiation, so that these algorithms usually perform poorly on images with non-uniform reflectivity. In this paper an adaptation for such algorithms is proposed. The strategy mainly consists of guiding the SFS algorithm through the image in order not to violate the typical albedo uniformity assumption. To do this, the pixels in the image are iteratively grouped into regions coming from the same scene until there are no more adjacent pixels satisfying this condition. The decision about the aggregation of a new pixel to a region is based on estimating its albedo and comparing it with the albedo of the region. During this process, SFS is applied only to the considered region and its results are used in the albedo estimation procedure. Some experimental results with synthetic and real images are discussed