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Questions tagged [opencv-features2d]

Must be used for extracting features from an image using OpenCV. Features are expressed in the form of points in OpenCV. A collection of feature points is called a descriptor. There are many algorithms to perform the same.

THIS LINK provides a list of available feature extracting algorithms in OPenCV. There is FAST, ORB, BRISK, etc. to name a few.

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SIFT & SURF : "module 'cv2.cv2' has no attribute 'xfeatures2d'" Set OPENCV_ENABLE_NONFREE CMake ==> Solution OpenCV 3 & OpenCV 4

I try to use the SIFT and SURF function with some of the versions of OpenCV 3 and openCV 4 (after having installed opencv-contrib-python) with: pip install opencv-contrib-python i try version 3.4.3 and 3.4.9 and 4.1.0, but have same probleme: sift…
RashidLadj_Winux
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undefined reference to `cv::DescriptorMatcher::knnMatch

I'm trying to use opencv native library in an android studio project. I get an error for undefined reference for the function knnMatch. I have added openCVLibrary to my project and had success to use other openCV features. Is there a specific why…
Nimrod Borochov
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Opencv - Features2D + Homography incorrect results

I have been having some issues getting the outline of the detected object in the correct place, its as if the coordinates are in the wrong place. I have the hessian set to 2000 and I have filtered for matches that are less than 3 times the minimum…
Juppal
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Extract common part of images with Opencv

I'm writing a program that find differences between images. For now, I'm finding features with AKAZE, so I've the common point of the 2 images. The problem is that these 2 images have only a part in common. How can I extract the common part from…
bjorn
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openCV4Android features2d error

I want to use features2d to draw good matches (not all matches) between two images.So I used this snippet of code: Mat gray1 = //image1 converted to gray Mat gray2 = //image2 converted to gray MatOfDMatch matches = new MatOfDMatch(); MatOfDMatch gm…
hasanghaforian
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Opencv drawKeypoints

Is drawKeypoints a free function? When I try to use it throws the following error cv.drawKeypoints is not a function I'm trying to write this…
Lusine Tamaryan
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OpenCV.js, build with ORB and features2d

I am trying to build a simple web/js app that would detect image on camera. I have already done this on iOS and Android using OpenCV so my obvious choice was to use OpenCV.js (latest release). I built opencv.js as in tutorial…
Dev_IL
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structure of opencv's hog output

I'm extracting the HOG features of a grayscale image using OpenCV's HOG implementation. Assuming that my image matches the default window size, i.e. 128x64, I'm struggling to understand correctly how that feature vector is organised. This is what I…
karl71
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OpenCV image descriptors to JSON

I want to store some image descriptors on a server so that when image matching on an android phone I can fetch the precomputed image descriptors rather then doing it on the fly. I have successfully created an application that can take an input image…
Juppal
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errors while compiling nonfree/features2d.hpp

I am trying to write a c++ program using the SIFT. I have already installed and built the opencv_contrib-master module as some have suggested that the latest version of OpenCV (version 3.0 which i have) doesn't have this module. I can physically…
newbie
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java opencv Features2d.drawMatches - Assertion failure or NullPointerException

I'm trying to create an image depicting matches between keypoints in images generated from sift files, using the Features2d.drawMatches method from openCV java API. I can't seem to figure out what kind of argument the method will take as an output…
NaN
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Error KAZE with opencv: Use of undeclared identifier

I tried to compile a function for extracting the features. Ptr kaze = KAZE::create(); But I get an errors with that. First is "Use of undeclared identifier 'KAZE'" The next line is kaze->detectAndCompute(img, noArray(), keypoints,…
Mani
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What is the best way to find SURF-features only on changed areas of frame?

For example, I calculate SURF descriptors for frames from real-time 50 fps FullHD video by using GPU: gpu::SURF_GPU But it is slow, and I can't calculate it for each frame, only for 10 fps. Video camera is stationary and fixed, so I can use the…
Alex
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C++ exception in cv::BFMatcher

I am having problems with the cv::BFMatcher when I try to perform the feature matching. I compute the descriptors with the xfeatures2D::SIFT descriptor. When I try to perform the matching the application output shows "Exception at 0x7ff833308b9c,…
Luis López
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VS2013 freezes as I type OpenCV include header files

I have a problem with VS2013. I'm trying to write a program in vc++ using opencv and in vs2013 update 4 IDE. the problem is as I just type these lines, my computer freezes. infact the hard activity runs to 100 percent and never stops untill restart.…
green-dev
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