contains material from
Template Matching Techniques in Computer Vision: Theory and Practice
Roberto Brunelli © 2009 John Wiley & Sons, Ltd
While the representation of image as rectangular arrays is the most widespread, alternative exists. Log-polar mapping, described in Section TM:2.4 is an example of space variant representation providing a spatial resolution decreasing from the center towards the boundary.
Log-polar mapping is usually obtained with specific sensors but can also be simulated via software to appreciate some of its characteristics. When we change the image representation from a (standard) rectangular lattice to a log-polar spatio-variant structure we are effectively performing a resampling task which is prone to aliasing if frequency content is not properly tuned. As log-polar sensor resolution is spatio-variant so must be the amount of smoothing applied before resampling. Usually, the two sensing structures are compared for a given maximum spatial resolution. In the case of a rectangular sensor the maximum resolution extends over the whole sensor while in the case of a log-polar sensor it is confined to the central (foveal) region.