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crop patch around SIFT point

asked 2013-07-22 02:21:16 -0500

mrgloom gravatar image

How to crop patch around SIFT(or other detector) point?

I want to crop image patch around detector point but I don't know how to determine size and scale (maybe orientation also matters?)

Is it makes sense or special point is only can be described by descriptor? I need this patches to visually inspect result of detections.

I want to get something like this http://www.vlfeat.org/demo/covdet_patches.jpg

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answered 2013-07-22 02:49:40 -0500

There is no evident size of "patch" around descriptors for SIFT. The number of octave is deduce from the image resolution, but if you only need a debug/feedback visualization, used the size you want... It doesn't really matter, as your patches are centered around the keypoints. If you want to do it fast, I suggest using a ROI to copy the parts of image to a destination buffer.

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what if I take something like Harris corner detector(no scale invariance) can I determine the size of patch?

mrgloom gravatar imagemrgloom ( 2013-07-22 05:29:45 -0500 )edit
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answered 2014-10-19 08:46:27 -0500

The octave is usually been set as 8 and there are also different scales of the original picture, this could be regard as filtered be different Gaussian filters. The patch I saw most is set as 44 or 22, each contains 44--66 pixals.

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Asked: 2013-07-22 02:21:16 -0500

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Last updated: Oct 19 '14