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Questions tagged [keypoint]

In computer vision field a keypoint is an interest point detected by the SIFT algorithm. Use this tag for programming issues related to the use of keypoints in the field of computer vision.

is an algorithm that finds "keypoints" in images that are robust to scale variations, perspective and lighting. In order to identify those keypoints, descriptors are generated basing on the surrounding pixels of the keypoint. This way, the same keypoints can be located in different images, which is called matching.

Programing questions related to keypoints in computer vision applications are an appropriate field for this tag.

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Facial Landmark Detection using Dlib

Is it possible to use train_shape_predictor_ex.cpp.html and face_landmark_detection_ex.cpp.html to training with different landmark numbers? Both detect 68 landmarks in a frontal face by default. I would like to detect 39 landmarks only. I can train…
RHV UFC
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What are KeyPoint and MatchDpoint in OpenCV in Java

Dears 1-I know the Point class is regarding two channel integer value coordinates(points): like MatOfPoint is a vector of integer points. Is it the same with the KeyPoint class? I know It is a class containing salient points.Is it true to look at…
Reza Ghoddosian
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Is there any way to do feature-based localization using OpenCV?

Im using OpenCV feature detection to estimate robot position based on comparison of LIDAR result and virtual map. I've try using orb feature detection followed by flannbasedmatcher, but the match result gone wrong. here's some of my code Ptr…
duck
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How to insert KeyPoints in MatOfKeyPoints

How do I build up a MatOfKeyPoint correctly? My code so far is: System.loadLibrary(Core.NATIVE_LIBRARY_NAME); String sourcePath = path; Features2d features2d = new Features2d(); Mat srcImgMat = Highgui.imread(sourcePath); MatOfKeyPoint mat = new…
Jürgen K.
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Accurate keypoint localization in SIFT

In his paper (Distinctive Image Feature from Scale-Invariant Keypoints), Lowe describes a way to get rid of "low contrast keypoints". This is done using a Taylor expansion up to the quadratic term: The extremum(xhat) is found, by taking the…
John Deer
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Show coordinated for each keypoints using flandmark (Javacv)

I am currently using this example from flandmark using JavaCV. Refer to: https://github.com/bytedeco/javacv-examples/blob/master/flandmark-demo/src/main/java/flandmark/Example1.java. I managed to run the code but is there a way that I could display…
Cael
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OpenCV+Android keypoint detection crash

I have made a big amount of research on this issue and tried all of them and none of them work, so it's time for a new topic on it. I am making a project where the user would select a picture from the device and the program would return the same…
equliser11
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How can I get Orientation Scale Position information of keypoints in OPENCV implementation?

I only can get image features form MAT file, but I also want some other information such as positions, orientation and scale. How can I get these information, could anyone offer its code? Thank you in advance.
neouyghur
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Get the SIFT descriptor for specified point using OpenCV

I want get the SIFT feature for specified points. These points is gotten by hand not by KeyPoint Detector. My question is: I only know the position of the points but have no idea about the size and angle value. How should I set this value? Here is…
tidy
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Surf feature Extraction

Objective: match blobs by using Surf descriptors and opencv 2.4.9 library. Algorithm: based on the following link: Steps #include #include #include "opencv2/core/core.hpp" #include "opencv2/features2d/features2d.hpp" #include…
Hani Goc
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Keypoint matching just works two times...? (java opencv)

I have a very strange problem. I'm using this code to detect an image in another one (java opencv): UPDATED CODE: public void startRecognition() { //load images, I want to find img_object in img_scene Mat img_scene =…
gemorra
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OpenCV/C++ - SIFT keypoint detection and corresponding descriptors

I have an image. I used Canny edge detector,and then I apply Sift on it. Here the result : I don't understand the result. Why have i some interest points on some black areas and not a lot where I expect the more ? Besides, what does the circle…
lilouch
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OpenCV - Display ONLY the keypoints NOT the image using SIFT

I am trying to only draw the keypoints (without the image) using this example code: import cv2 import numpy as np img = cv2.imread('test.png') gray= cv2.cvtColor(img,cv2.COLOR_BGR2GRAY) sift = cv2.SIFT() kp =…
digit
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OpenCV 3.0 missing methods like drawMatches and drawMatchesKNN

I've recently updated to OpenCV 3.0 tp2 on Python(2.7), to avail of the methods like drawMatches and drawMatchesKnn(), but neither seem to be available. I built from source, and everything installed correctly, but I still don't have the methods. I…
Crackers91
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Image Processing - Detection of joint features in volumetric wire-like shapes (fibres)

I am dealing with some research on the analysis of fibres in Steel fibre reinforced concrete, and after a few months on an automatic research based on the analysis of the hessian matrix for each pixel, i find myself stuck. The above mentioned…
drHogan
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