1. An image retrieval system comprising: an image entry unit configured to receive as input an image; a descriptor determining unit configured to transform the image into an intermediate image to generate a descriptor of the image; an image comparing unit configured to compare the image with one or more candidate images by comparing the descriptor of the image with descriptors of said one or more candidate images; and a retrieving unit configured to retrieve at least one of said one or more candidate images similar to the image based on the comparison of their descriptors.