Stack Overflow
Stack Overflow

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.

187 questions
91
votes
2 answers

What are keypoints in image processing?

When using OpenCV for example, algorithms like SIFT or SURF are often used to detect keypoints. My question is what actually are these keypoints? I understand that they are some kind of "points of interest" in an image. I also know that they are…
dephinera
  • 3,703
  • 11
  • 41
  • 75
21
votes
1 answer

What is difference between features and keypoints in computer vision?

I am studying something about some possibilities of OpenCV object detection and this is confusing to me. I just don't see the difference between these two.
matogolf
  • 221
  • 2
  • 4
19
votes
2 answers

OpenCV return keypoints coordinates and area from blob detection, Python

I followed a blob detection example (using cv2.SimpleBlobDetector) and successfully detected the blobs in my binary image. But then I don't know how to extract the coordinates and area of the keypoints. Here are the code for the blob detections: # I…
J_yang
  • 2,672
  • 8
  • 32
  • 61
10
votes
4 answers

Visualizing OpenCV KeyPoints

I am learning OpenCV and at the moment I am trying to understand the underlying data stored in a KeyPoint so that I can better utilize that data for an application I'm working on. So far I have been going through these two…
jstaker7
  • 1,226
  • 4
  • 15
  • 29
9
votes
1 answer

orb detect crashes when try to detect

I am trying to create a basic image detector with open cv. I am using ORB, I try to open an image and then I try to detect keypoints in the image. Here is my code import cv2 from cv2 import ORB image1 = cv2.imread("original.jpg",…
Yedidya kfir
  • 1,419
  • 3
  • 17
  • 32
8
votes
0 answers

Matching specific elements of an Image; known shapes OpenCV C++

After getting no answer to this question, I ended up coming across some interesting looking possible solutions: The Robust Matcher from this post, as well as the Canny Detector from this post. After setting up a Canny Edge Detector, referencing its…
MLMLTL
  • 1,519
  • 5
  • 21
  • 35
8
votes
2 answers

how to improve keypoints detection and matching

I have been working a self project in image processing and robotics where instead robot as usual detecting colors and picking out the object, it tries to detect the holes(resembling different polygons) on the board. For a better understanding of the…
SidJaw
  • 133
  • 2
  • 10
6
votes
2 answers

How to extract keypoints from Harris Corner Detector using Opencv

First I would use cv::cornerHarris() to detect the corners (which i could do easily). Second I want to extract keypoints from Harris detector and store them in std::vector (which i have no idea how to do). I will use this later to…
HM Moniruzzaman
  • 135
  • 1
  • 11
6
votes
1 answer

Python : Feature Matching + Homography to find Multiple Objects

I'm trying to use opencv via python to find multiple objects in a train image and match it with the key points detected from query image.For my case, i'm trying to detect the tennis courts in the image provided below. I I looked at the online…
Reward
  • 87
  • 1
  • 5
5
votes
2 answers

convert keypoints to mat or save them to text file opencv

I have extracted SIFT features in (opencv open source) and they are extracted as keypoints. Now, I would like to convert them to Matrix (With their x,y coordinates) or save them in a text file... Here, you can see a sample code for extracting the…
Mario
  • 1,469
  • 7
  • 29
  • 46
5
votes
1 answer

How to prepare a custom keypoints dataset for WongKinYiu/Yolov7 Pose Estimation?

How do I prepare a custom keypoints dataset for WongKinYiu/yolov7?
C.Tale
  • 263
  • 2
  • 13
5
votes
1 answer

Performance issues using BRISK detector/descriptor OpenCV

I'm experiencing a performance problem when I use BRISK for feature detection and description in OpenCV. Basically I try to match all the descriptors I get from this image: against all the descriptors I get from a database of images using flann…
Maximus
  • 165
  • 1
  • 7
5
votes
2 answers

drawing a line between feature points without using "drawmatches" function

I got the feature points from two consecutive by using different detectors in features2d framework: In the first frame, the feature points are plotted in red In the next frame, the feature points are plotted in blue I want to draw a line between…
sy456
  • 1,644
  • 2
  • 14
  • 16
5
votes
2 answers

what is the meaning and use of class member class_id of class cv::KeyPoint in opencv?

In reference manual of OpenCV 2.4.3 KeyPoint::class_id is described as "object id that can be used to clustered keypoints by an object they belong to". Due to lack of my adequate knowledge about 'keypoint' I can't understand whats the purpose of…
Sohorab Hossain
  • 368
  • 1
  • 12
4
votes
1 answer

why is FAST/ORB bad at finding keypoints near the edge of an image

ORB doesn't find keypoints near the edge of an image and I don't understand why. It seems worse that SIFT and SURF and I would expect the opposite. If I understand correctly then SIFT/SURF use a 16x16 and 20x20 square block respectedly around the…
Haydon Berrow
  • 485
  • 2
  • 6
  • 14
1
2 3
…
12 13