Efficient content-based retrieval in image databases: a probabilistic approach

This paper describes the retrieval process from image databases, based on a partial match between the query and the images. The proposed approach allows to measure the similarity between the query and the images in the database and to retrieve those having the highest probability to be relevant. The paper describes the query processing and the access structures, based on the `signature method'. Four levels of signature files are associated to the image database and a signature is associated to the query. The query signature is compared with the image signatures in a four step image processing algorithm. The result of the process is a set of images with an associated recognition degree, measured by using information provided by the user during query formulation (such as importance of the presence of each object) and by using the image structure and the recognition degree associated to each object. The retrieved images are presented to the user in decreasing relevance order. The method described so far is inefficient, since the selection of most relevant images is executed among all relevant images (even those having a low relevance). The paper presents two approaches for improving the efficiency of query processing by (a) reducing the number of accesses to the Image Database and (b) by reducing the number of accesses to the signature file. The two approaches are discussed in detail in the paper. The advantages and drawbacks of each method are illustrated.