A method is presented for estimating the orientation of a textured surface as a descriptor of surface shape. It is based on the analysis of local spectrum information of the texture in an image. The local spectrum representation is computed by the two-dimensional Wigner distribution, which gives the spatial-frequency information as a function of location. The change in texture density, or the so-called texture gradient, caused by the perspective projection of a surface in the three dimensional world onto the two-dimensional image plane, is computed from this space-frequency representation by measuring the high-frequency energy distribution at each location of the image. The surface orientation is then estimated from the texture gradient. This method was implemented for the limited case of planar surfaces. Simulations were performed and results were analyzed to address issues related to the method's estimation accuracy, implementation, and limitations.>