1. An image processing method comprising the steps of: obtaining a weighting parameter for a statistical characteristic quantity representing a degree of sharpness in a predetermined structure in an input image by fitting a model representing the structure to the structure in the input image, the model obtained by carrying out predetermined statistical processing on a plurality of images representing the predetermined structure in different degrees of sharpness, and the model representing the structure by one or more statistical characteristic quantities including the statistical characteristic quantity representing the degree of sharpness and by weighting parameter or parameters for weighting the statistical characteristic quantity or quantities according to an individual characteristic of the structure; and adjusting sharpness in at least a part of in the input image according to a value of the obtained weighting parameter.