RECONSTRUCTION OF SHAPE FROM SHADING IN COLOR IMAGES

We propose a method for shape reconstruction from color shades produce d by multiple chromatic light sources. The linear relation between sur face-normal vectors and three-dimensional response vectors for a unifo rmly colored and illuminated region of a surface can be reconstructed in two steps. In the first step a quadratic form of metric in response space induced from a natural metric in normal space is reconstructed. At this stage proper image segmentation can be obtained. In the secon d step an exact mapping from response space into the space of surface normals is reconstructed. The matrix for this mapping is one of the sq uare roots of the quadratic-form matrix that satisfies the integrabili ty constraint. The method is in all respects much simpler than existin g methods for solving the depth-from-shading task for monochromatic im ages.