1. An image processing method for recovering a predetermined missing element in a structure represented in an input image, the method comprising the steps of: obtaining weighting parameters for statistical characteristic amounts corresponding to the structure in the input image by applying the structure in the input image to a model representing an object which belongs to the same category of matter as that of the structure in which the element missing in the input image is present, the model obtained by performing predetermined statistical processing on a plurality of images each representing an object which belongs to the same category of matter as that of the structure in which the element missing in the input image is present, and the model representing the object by one or more statistical characteristic amounts representing components in the structure in which the element missing in the input image is present and by one or more weighting parameters for weighting the statistical characteristic amounts based on a characteristic specific to the structure; and generating an output image in which the missing element has been recovered based on the obtained weighting parameters and the statistical characteristic quantities.