Peano key rediscovery for content-based retrieval of images
Youssef Chahir, Liming Chen · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1997
Currently the most content-based retrieval methods of images are based on global features like histograms. Few methods have considered the spatial information for the indexing and query purpose. In this paper we present an efficient multi-dimensional spatial indexing method based on the Peano key ordering of spatial locality of regions. The Peano order gives a direct mapping between an integer and its corresponding element in the multi-dimensional space. The position in the ordering of each region in an image can be simply determined by interleaving the bits of the x and y coordinates of the region. In our method, global features of the query image like histograms of colors are first used to eliminate images in the database, which are not similar. Then the query is decomposed into a quadtree in order to extract characteristics, for instance predominant colors, associated with each square. These spatial information are identified by a list of Peano keys. This list constitutes a spatial signature of the query image. This spatial signature is researched into candidate images. For a given candidate image, each Peano key of the signature precisely indicates the spatial region whose characteristics are compared to the ones associated with the Peano key. The main advantages of our method are twofold: first its generality since it allows to associate spatial information to every kind characteristics of images, second its efficiency because there is no need to pre- extract characteristics from images in the database.