1. An image processing system comprising: individual data generation means for generating individual 3-dimensional shape data representing the 3-dimensional shape of an individual object and individual texture data representing the texture of the individual object based on a 3-dimensional shape parameter and texture parameter using a generalized 3-dimensional object model which is calculated based on 3-dimensional shape data and texture data of a plurality of objects similar to one another; first illumination basis calculation means for calculating an individual illumination basis representing a variation in the luminance value of each portion of the 3-dimensional surface of the individual object under various illumination conditions based on the individual 3-dimensional shape data and individual texture data generated by the individual data generation means; reproduced image generation means for generating a reproduced image which is an image reproducing the same illumination condition as an input image using the individual illumination basis group calculated by the first illumination basis calculation means; and parameter update means for repeatedly updating the 3-dimensional shape parameter and texture parameter to be given to the generalized 3-dimensional object model such that the reproduced image generated by the reproduced image generation means is close to the input image until a predetermined convergence condition is satisfied.