Shape from Color

We present a method for recovering the shape of a single Lambertian surface, with unknown but uniform re ectance, from a single RGB image of the object. The method depends upon the linearity of the relationship between RGB sensor responses and surface normal directions that stems from the Lambertian model. The algorithm follows closely upon work on the photometric stereo method. However, that method requires as input three separate black and white intensity images, each taken separately, whereas the method set out here needs only one color image. For the method to succeed, the lighting color must vary with direction from the surface. We test the method by including three separate point light sources all contributing to the illumination of the scene. The method correctly recovers surface normals, up to an overall orthogonal transformation. 2 Shape from Color 3