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rotational symmetry

asked 2013-02-27 09:12:06 -0500

rob123 gravatar image

Hi there,

I am currently writing a project in c and I need to be able to analyse a png file and determine whether it has any rotational symmetry, is this possible using opencv?

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answered 2013-02-27 11:59:29 -0500

Rotational symmetry is a nice play around thingy. Simply said, an approach that you could use is template based matching. There are some general steps to take in order to perform this.

  1. Rotate a given image (imgBase) for some degrees and call it imgRotated
  2. For the first image, define some interesting points by performing an interesting feature point detector like SURF, SIFT, ORB, ...
  3. Use a set of features defined on the imgBase as locations for test. Feed regions of interest around those points as templates to a descriptor and create a representation for it. Many aproaches are here possible, look at this link : http://docs.opencv.org/modules/gpu/doc/feature_detection_and_description.html
  4. Apply same descriptor at same locations in imgRotated
  5. Match the descriptors for each point and define the amount of equality which will be an amount of rotational symmetry.

I do not have a solution, but given this comments, I think you got some starting points right.

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This implies that you know the rotation axis... I would expect that this knowledge is not available in many cases.

SR gravatar imageSR ( 2013-02-28 05:33:38 -0500 )edit

I was indeed asuming that the rotation axis was the centerpoint of the object and 2D objects. Another approach, I have no single clue :P

StevenPuttemans gravatar imageStevenPuttemans ( 2013-02-28 05:54:26 -0500 )edit
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Asked: 2013-02-27 09:12:06 -0500

Seen: 652 times

Last updated: Feb 27 '13