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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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Why Sift Feature Detector cannot detect key points for some images?

I am reading images from a set and extracting their features. However, for some images(very few, around 4 per mille), SiftFeatureDetector::detect( image, keypoints) cannot detect key points and returns me an empty set of key points. When I tried…
Aka
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Working with large (over 2000x2000) images in Dlib, and they don't fit in my screen

So after a few weeks, I finally managed to get Dlib installed, and immediately ran into another problem. I downloaded and ran their face landmark dector: http://dlib.net/face_landmark_detection.py.html and while the actual program works fine, when I…
Rich
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Keypoints Analysis with C++ and OpenCV

I have a question about the following code: #include "iostream" #include #include #include #include #include…
user3429953
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opencv keypoints -1.#IND

Boy, do I need some help! I need to iterate over the detected keypoints accessing the x, y, and size fields of each keypoint. The code I am using is almost all copied from tutorials. Here is a section of the code where I'm having trouble. // Draw…
user1247254
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Loading keypoints and drawing

I have a piece of code that calculates the SURF keypoints of an image and saves them to a yml file. I am then trying to load that file and draw the saved keypoints on am image. Keypoint and write code: cv::Mat img_1 = cv::imread(argv[1],…
Colin747
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Display Keypoints on Image in Android - OpenCV

I'm trying display a image with keypoints detected. In my code, i get a list of key points, my i can't display the image on screen. I think that my problem is on converting the image to bitmap from MAT. What i'm doing wrong ? Here is my code: …
NatsuDragonEye
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Matching photographed image with screenshot (or generated image based on data model)

first of all, I have to say I'm new to the field of computervision and I'm currently facing a problem, I tried to solve with opencv (Java Wrapper) without success. Basicly I have a picture of a part from a Model taken by a camera (different angles,…
gemorra
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OpenCV not generating descriptors

I am trying to use OpenCV for generating descriptors at keypoints in an image on iOS. I have done feature detection using my own algorithm and now want to extract the descriptors at these points. I implemented the following code to do this: cv::Mat…
System123
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How to determinate object position with openCV in the world coordinate

I'm trying to implement a task for the robotic class of my university. The main task of the project it's to grasp a cup with the KUKA-youbot robot. The main problem that i found it's about the part of vision computing of the project. More precisely,…
luke88
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How to draw keypoints onto input image using matlab?

This question is regarding SIFT features and its use in MATLAB. I have some data containing the following information: The x,y co-ordinates of each feature point The scale at each feature point The orientation at each feature point The descriptor…
user3168226
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keypoints match between using optical flow

I have two pictures PlanA : I detect SIFT key poitns in picture A and using optical flow to find the corresponding points in picture B Plan B: but if i detect SIFT key points in picture B and do the match thing between picture A and picture B What…
Moore liu
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use of sift keypoint radius in calculating feature vector

I have followed many tutorials on SIFT and have a good understanding of how key points are detected.But while extracting SIFT feature vectors where does the keypoint scale play the role. As I understood, we just take a 16 X 16 window around a…
code4fun
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detecting image keypoints --javaCV --EXCEPTION_ACCESS_VIOLATION

I'm java developer .My goal is to detect image keypoints using javaCV this is my code : final CvMat image1 = cvLoadImageM("im1.png" , 0); final CvMat image2 = cvLoadImageM("im2.png", 0); SIFT sift = new SIFT(); …
nawara
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how to decrease number of descriptors when using SIFT?

I have used SIFT to find keypoints and descriptors,now I want to decrease number of descriptors because for example for an image with size 256x256 it gives me 120000 descriptors which is time consuming. please let me know any suggestion how to…
user615864
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OpenCV STIP (space time interest points)

Where can I get the source code of Laptev's STIP (space-time interest points)? On his webpage only the executables are provided. Thank you in advance.
user1343279
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