Learning Sparse Overcomplete Codes for Images |
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Authors: | Joseph F Murray Kenneth Kreutz-Delgado |
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Affiliation: | 1. Brain and Cognitive Sciences Department, Massachusetts Institute of Technology, 77 Massachusetts Ave. 46-5065, Cambridge, MA, 02139, USA 2. Electrical and Computer Engineering Department, University of California, San Diego, 9500 Gilman Dr. Dept 0407, La Jolla, CA, 92093-0407, USA
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Abstract: | Images can be coded accurately using a sparse set of vectors from a learned overcomplete dictionary, with potential applications in image compression and feature selection for pattern recognition. We present a survey of algorithms that perform dictionary learning and sparse coding and make three contributions. First, we compare our overcomplete dictionary learning algorithm (FOCUSS-CNDL) with overcomplete independent component analysis (ICA). Second, noting that once a dictionary has been learned in a given domain the problem becomes one of choosing the vectors to form an accurate, sparse representation, we compare a recently developed algorithm (sparse Bayesian learning with adjustable variance Gaussians, SBL-AVG) to well known methods of subset selection: matching pursuit and FOCUSS. Third, noting that in some cases it may be necessary to find a non-negative sparse coding, we present a modified version of the FOCUSS algorithm that can find such non-negative codings. Efficient parallel implementations in VLSI could make these algorithms more practical for many applications. |
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