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How to use the dense sampling detector to image with OpenCV3_python?

asked 2016-09-16 03:41:49 -0500

gelgel gravatar image

I am using python2.7, OpenCV3 with opencv-contrib to image processing.
So I can use SIFT and get features as follows,

sift = cv2.xfeatures2d.SIFT_create()
kp = sift.detect(gray,None)
des = sift.compute(gray,kp)

This is good.
Now "kp" is the keypoint that result computed by SIFT's feature detector.
But I want to change this detector to dense(grid) sampling detector like this. https://www.safaribooksonline.com/lib...
and I want to compute descriptors with "sift.compute(gray,kp)"
please help me.
Note: previously, it seems this is available "dense = cv2.FeatureDetector_create("Dense")"

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answered 2016-09-16 04:04:12 -0500

berak gravatar image

the "Dense", "Pyramid", "Adaptive" detector variants were all removed in opencv3. (though you can still iterate over a grid, and add your own keypoints)

also, you should rather use sift.detectAndCompute() for efficiency (else you're throwing away half of the computation)

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Thank you for answering. "the Dense was removed..." It is sad. I understand I have to create my own detector. But I don't know how add the keypoints properties to my own detector like a list, list = [(5,5),(10,10),...] Please tell me how. Or, I have to create in xfeatures2d.hpp before make cv2.so files?

gelgel gravatar imagegelgel ( 2016-09-16 04:41:11 -0500 )edit

Fixed my code to "sift.detectAndCompute()",thank you!

gelgel gravatar imagegelgel ( 2016-09-16 04:47:37 -0500 )edit

if you want to use your own keypoints, the list should look like:

[
    cv2.KeyPoint(x1,y1,radius),
    cv2.KeyPoint(x2,y2,radius),
    ...
]

(then, ofc, use sift.compute() with that ! :)

berak gravatar imageberak ( 2016-09-16 05:16:17 -0500 )edit
1

The problem was solved with your help. I'm so glad!
Thank you very much!

gelgel gravatar imagegelgel ( 2016-09-16 05:29:36 -0500 )edit
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Asked: 2016-09-16 03:41:49 -0500

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Last updated: Sep 16 '16