Questions tagged [feature-detection]

Feature detection is a process in computer vision that aims to find visual features within the image with particular desirable properties. Detected features can be points, image regions or continuous curves in the image. Interesting properties can include invariance to noise, perspective transformations, or properties interesting for specific usages (e.g. tracking).

Feature detection is a process in computer vision that aims to find visual features within the image with particular desirable properties.

Detected features are some subsection of the image, and can be:

  • points (e.g. Harris corners)
  • connected image regions (e.g. DoG or MSER regions)
  • continuous curves in the image

Interesting properties can include invariance to noise, perspective transformations and viewpoint changes (camera translation and rotation), scaling (for use in visual feature matching), or properties interesting for specific usages (e.g. visual tracking).

Important information about visual features can include:

  • coordinates in the image
  • radius of the visual feature
  • scale (octave) of the image on which the feature has been extracted

After detecting the feature with some feature detection algorithm, it is usually described by a descriptor vector (several known descriptors are used today) for the purposes of visual feature matching, while the feature's position in the image can be used directly for application in tracking.

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How to make KAZE features detect corners?

I'm struggling to control the interest points in KAZE detector. I only want the detector to extract the corner/interest points. What parameters do I tweak to get the desired results? This is my code: img = imread("") I = rgb2gray(img); points =…
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Counting number of bright spots in image (python)

I'm trying to develop a way to count the number of bright spots in an image. The spots should be gaussian point sources, but there is a lot of noise. There are probably on the order of 10-20 actual point sources in this image. My first though was to…
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Code to detect mobile browser support for HTML5

I want the code (C# / JavaScript) to detect which mobile browsers are support HTML5. I have the code to detect the HTML5(canvas) compatibility for desktop browsers. But this code is not working for mobile browsers. if…
Sathish
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Detect drag&drop support on mobile browsers

Caniuse says that Firefox for Android (v63) does not support drag&drop. Which is understandable since drag&drop doesn't make much sense on a single-app mobile screen. But the corresponding events are defined on several elements. How can I detect…
ygoe
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Significance of sobel's scale when searching Harris corners

For function cornerEigenValsVec in corner.cpp, I am stuck on understanding effects of local variable scale passing to Sobel(from line 257 to line 263): int depth = src.depth(); double scale = (double)(1 << ((aperture_size > 0 ? aperture_size : 3) -…
Finley
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Only apply CSS if not Internet Explorer

CSS in this media query is only used when Internet Explorer is detected (simplifying the standard implementation for brevity): @media screen and (-ms-high-contrast: none) { body { background-color: purple; } } The way I understand how this…
spiderplant0
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Feature Matching using OpenCV ORB not giving satisfactory results all the time

I'm using OpenCV ORB for checking whether two images are similar or not. ORB is efficient and gives me best results most of the time. But, in some cases, ORB's output is not satisfactory. I'm using distance parameter, got after KnnMatch, to identify…
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Can Canny edge detection be used in Hog feature extraction?

As I studied so far Canny is an edge detection algorithm and Hog is a feature extraction method. In openCV I saw some implementation of Hog feature extraction with Sobel kernels: import numpy as np import cv2 img = cv2.imread("") img =…
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ORB vs FAST detectors

I'm trying to detect Keypoints all over the image so I tried dividing it into cells and detect on each cell. However, I didn't get the same results using ORB detector as using FAST detector. For ORB, I get way lesser Keypoints as I increase the…
user6099747
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How to detect if Oracle database supports auto increment?

I'm working on a project in which we may be using an Oracle 11g or an Oracle 12c database depending on what's available in various environments -- not ideal I know :( My project is a Spring Boot application and I'm using Liquibase to manage the…
MattWeiler
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Want to detect features and match the feature in 2 different frames

I'm currently using OpenCV 3.4.0, c++ in QT creator. I've tried sample code in this page https://docs.opencv.org/2.4/doc/tutorials/features2d/feature_description/feature_description.html int minHessian = 400; cv::xfeatures2d::SurfFeatureDetector…
Hyunjun
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The receptive field of feature maps in CNN is overlapped. How does this affect?

The receptive field of a feature map in a convolutional neural network is repeated.What is the impact of such repeated calculations?Some people say that this is a repeated calculation for the original graph? How to understand it?I know this may be a…
gaoyang
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OpenCV: Feature Matching + Homography Help to tune results

I am looking for some help in fine tuning the results of using Feature Matching and Homography, as described in this tutorial. I am trying to use the approach described in the article to crop and deskew faxed/scanned forms, as a preprocessing step…
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cv2 SIFT + Brute force matching not giving good results

So I'm trying to overlay a thermal image with an rgb image using SIFT to match features and homography so that I can overlay them later on. The code I have works with about 50% of the thermal/rgb sets I have but many sets, such as this one, give…
Mr Boss
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Feature detection wavefront object using python. is there any libraries?

I am doing a 3D Scan and export the result as a wavefront object (.obj with the mesh, and .mtl and .jpeg for the texture). the link between the faces of the mesh and the texture are in the .obj. I am trying to detect "circles" for example on the 3D…
p.deman
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