The Computer Journal Advance Access originally published online on April 20, 2007
The Computer Journal 2009 52(1):15-30; doi:10.1093/comjnl/bxm008
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Example-Based Regularization Deployed to Super-Resolution Reconstruction of a Single Image
Department of Computer Science, The Technion—Israel Institute of Technology, Haifa 32000, Israel
* Corresponding author: elad{at}cs.technion.ac.il
Received 11 May 2006; revised 28 October 2006
In super-resolution (SR) reconstruction of images, regularization becomes crucial when insufficient number of measured low-resolution images is supplied. Beyond making the problem algebraically well posed, a properly chosen regularization can direct the solution toward a better quality outcome. Even the extreme case—a SR reconstruction from a single measured image—can be made successful with a well-chosen regularization. Much of the progress made in the past two decades on inverse problems in image processing can be attributed to the advances in forming or choosing the way to practice the regularization. A Bayesian point of view interpret this as a way of including the prior distribution of images, which sheds some light on the complications involved. This paper reviews an emerging powerful family of regularization techniques that is drawing attention in recent years—the example-based approach. We describe how examples can and have been used effectively for regularization of inverse problems, reviewing the main contributions along these lines in the literature, and organizing this information into major trends and directions. A description of the state-of-the-art in this field, along with supporting simulation results on the image scale-up problem are given. This paper concludes with an outline of the outstanding challenges this field faces today.
Key Words: Regularization • example-based • nearest neighbor • Bayesian reconstruction • MMSE • MAP • PCA • clustering • K-D tree • scale-up • super-resolution