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Is FREAK scale and rotation invariant?

asked 2012-08-03 21:22:44 -0500

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I've read news about FREAK in OpenCV 2.4.2. Is FREAK scale and rotation invariant, like SURF? Is it as good as SURF?

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Goodness is a relative measure - you should try both of them for your specific situation, and choose the best trade-off between quality, speed, and probably other factors.

sammy gravatar imagesammy ( 2012-08-06 03:15:48 -0500 )edit

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answered 2012-09-18 05:06:35 -0500

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SURF is a detector like FAST. FREAK is a descriptor extractor. It has more sense to compare it with SIFT.

Actually, in the paper they say they use FREAK descriptors together with a pyramidal FAST detector that is called AGAST.

So answering your question:

  • It is rotation and scale invariant.

  • It is supposed to be a more robust descriptor than SIFT. I am going to test it but still don't have results.

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SURF isn't just a detector (which uses the fast-hessian method), it also is a descriptor. You can extract 64 or 128 dimensional descriptors from your detected keypoints.

Ben gravatar imageBen ( 2012-11-05 12:15:13 -0500 )edit
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answered 2012-08-05 21:05:19 -0500

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Hi!

I recommend you to read the paper FREAK: Fast Retina Keypoint. Alahi et al. CVPR2012.

The authors claim that FREAK is scale and rotation invariant and even more robust than SURF.

I hope this helps.

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answered 2012-11-05 11:26:09 -0500

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It's actually a little bit more subtle: the pairs used by FREAK were chosen for their matching performance after a scale-sensitive detection of keypoints (the KP detector used is the same as BRISK, i.e. a multi-scale FAST + orientation detection). Hence, FREAK is rotation and scale invariant only up to the sensitivity of this detector and is not per se invariant.

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Asked: 2012-08-03 21:22:44 -0500

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Last updated: Nov 05 '12