Invariance in content-based retrieval

The paper discusses the role of invariance in content-based image retrieval, and discusses future directions. In the repertoire of images under consideration, a narrow domain is a set of images containing a limited variety in the object´s appearances. In a narrow domain, the recording circumstances typically are similar or standardized over the whole domain. On the other end of the spectrum is a broad domain with a large variety in recording circumstances and appearances. The sensory gap between the object in the world and the information captured from a recording causes unwanted variance in the description of an object. We list conditions of variance, and we review some of features which are invariant under these conditions