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How to get the descriptor value from "SiftDescriptorExtractor"?

asked 2012-09-03 02:23:07 -0500

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I use SiftDescriptorExtractor to compute the descriptors of keypoints. I'm trying to get the descriptor value. Does someone know how to do it?

(PS:My opencv version is 2.4.2)

This is the part of the code

//-- Step 2: Calculate descriptors (feature vectors)
SiftDescriptorExtractor extractor;
Mat descriptors_object, descriptors_scene;
extractor.compute( img_object, keypoints_object, descriptors_object );
extractor.compute( img_scene, keypoints_scene, descriptors_scene );
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I don't understand the question. What's the descriptor value? A descriptor is a fixed-size vector and every row in your descriptors matrix corresponds to such a vector.

Ben gravatar imageBen ( 2012-09-03 11:45:11 -0500 )edit

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answered 2012-09-05 03:39:20 -0500

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You can get pointer to descriptor vector via ptr method:

Mat descriptors;
float* descVector = descriptors.ptr<float>(i); // i - feature index
// it will have descriptors.cols size
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answered 2012-09-05 01:48:42 -0500

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oh! What I'm talking about is how to get every vector because I want to use that to do image matching by myself.

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answered 2012-09-08 12:26:55 -0500

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thanks for your help!

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Asked: 2012-09-03 02:23:07 -0500

Seen: 1,128 times

Last updated: Sep 08 '12