1. A method for searching image data representing an image from a database by using a query image, the image data including information indicative of a shape of a contour of the image, comprising: obtaining a query image data representing the query image; extracting information indicative of a shape of a contour of the query image; and determining the image data in the database on the basis of correlation of the topological characteristics of the shapes of the contours of the images and the query image.