Image compression using principal component neural networks

Principal component analysis (PCA) is a well-known statistical processing technique that allows to study the correlations among the components of multivariate data and to reduce redundancy by projecting the data over a proper basis. The PCA may be performed both in a batch method and in a recursive fashion; the latter method has been proven to be very effective in presence of high dimension data, as in image compression. The aim of this paper is to present a comparison of principal component neural networks for still image compression and coding. We ®rst recall basic concepts related to neural PCA, then we recall from the scienti®c literature a number of principal component networks, and present comparisons about the structures, the learning algorithms and the required computational efforts, along with a discussion of the advantages and drawbacks related to each technique. The conclusion of our wide comparison among eight principal component networks is that the cascade recursive least-squares algorithm by Ci-chocki, Kasprzak and Skarbek exhibits the best numerical and structural properties. q 2001 Elsevier Science B.V. All rights reserved.