1. An image processing method comprising the steps of: separating first image data of a two-dimensional image into image data of objects and image data of background; obtaining feature amounts of two-dimensional objects from the image data of objects; comparing the feature amounts of the two-dimensional objects with data stored in a database; determining front-back relations among the two-dimensional objects using results of the comparisons, based on proximity of the two-dimensional objects with regard to a front side of the two-dimensional image; processing the image data of the two-dimensional objects according to the front-back relations among the two-dimensional objects; and combining the image data of the two-dimensional objects after the processing with the image data of the background to generate second image data in which a sense of depth or stereoscopic effect is increased compared to the first image data.