On the Source of Asymmetry in Image Registration Problems

Goksel Dedeoglu and Takeo Kanade
tech. report CMU-RI-TR-05-17, Robotics Institute, Carnegie Mellon University, May, 2005


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Abstract
Most image registration problems are formulated in an asymmetric fashion. Given a pair of images, one is implicitly or explicitly regarded as template, and warped onto the other to match. In this paper, we focus on this seemingly arbitrary choice of the roles, and reveal how it may lead to biased warp estimates in the presence of relative scaling. We present a principled way of selecting for the template, and explain why only the correct asymmetric form, with the potential inclusion of a blurring step, can yield unbiased estimators. Our analysis also shows that commonly-used symmetrization/regularization of the warps may actually lead to biased estimators. We experimentally validate our analysis by measuring the bias of L1 and L2 norm motion estimators when the template choice is wrong, and conclude that image registration is inherently an asymmetric problem.

Keywords
Image registration, Resolution, Asymmetry, Estimation Bias

Notes
Associated Center(s) / Consortia: Vision and Autonomous Systems Center
Number of pages: 18

Text Reference
Goksel Dedeoglu and Takeo Kanade, "On the Source of Asymmetry in Image Registration Problems," tech. report CMU-RI-TR-05-17, Robotics Institute, Carnegie Mellon University, May, 2005

BibTeX Reference
@techreport{Dedeoglu_2005_5296,
   author = "Goksel Dedeoglu and Takeo Kanade",
   title = "On the Source of Asymmetry in Image Registration Problems",
   booktitle = "",
   institution = "Robotics Institute",
   month = "May",
   year = "2005",
   number= "CMU-RI-TR-05-17",
   address= "Pittsburgh, PA",
}