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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Using SIFT (or an alternative) in Python OpenCV 4.2.0 (In 2020)

I am trying to use SIFT for feature detection with Python, but it is no longer part of OpenCV or OpenCV contrib. With OpenCV opencv-contrib-python (both versions 4.2.0.34, the latest as of this question), I get: >>> import cv2 >>>…
Salvatore
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How to implement KAZE and A-KAZE using Python and OpenCV?

I am trying to implement KAZE and A-KAZE using Python and OpenCV for Feature Detection and Description on an aerial image. What is the code? Also, what descriptor should go along with it for Feature Matching?
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How to implement BRISK using Python and OpenCV to detect features?

I want to implement BRISK using Python and OpenCV for Feature Detection and Description in drone images. Since BRISK is also a descriptor, I want to use its description features to match two images. How do I do it?
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How do I split a shape with conected pixels in to two parts in a binary image

My goal is to draw a rectangle border around the face by removing the neck area connected to the whole face area. All positive values here represent skin color pixels. Here I have so far filtered out the binary image using OpenCV and python. Code…
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JavaScript redirect causes undesired search engine results

I have an HTML5 demo site (http://html5beats.com/) that uses JavaScript to detect certain HTML5 features. I do a redirect to a "please change or upgrade your browser" page if those features are not present, since they are critical to making the…
Andy West
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How to choose the estimation algorithm for the findHomography() function?

In OpenCV, Why choose RANSAC instead of LMeDS or RHO? What advantages and disadvantages does each have? In which cases should each one be chosen? This question came up when I read the tutorial "Features2D + Homography to find a known object" Thanks…
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How to extract color features via histogram from a masked image?

I extracted an object from an image, so now I have a masked image with a tennis ball and a black background. I want to extract the color features from the tennis ball alone via a histogram. This is the code I have so far, but by the looks of the…
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What's the best CSS property for detecting browser support for selectors

I'm writing some Modernizr extensions to detect browser support for things such as :first-child, :last-child in CSS. In order to do so I'm applying a style and then checking to see if teh element has that style. What's the most-reliable CSS property…
wheresrhys
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opencv feature matching with empty formular template

i've been trying to match a scanned formular with its empty template. The goal is to rotate and scale it to match the template. Source (left), template (right) Match (left), Homography warp (right) The template does not contain any very…
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Error: 'uncaught_exceptions' is unavailable: introduced in macOS 10.12

I'm testing for a problem that surfaced recently during testing under C++17. Here is the source file: $ cat test.cxx #if __EXCEPTIONS && __has_feature(cxx_exceptions) # include # define CXX17_EXCEPTIONS 1 #endif void Foo() { #if…
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Performing Feature Matching of Images in Java

I'm trying to perform feature matching on images in Java. The code example for this I found is this one. I fixed the FeatureDetector deprecation via this answer. However, when I use this code, it does not detect a sub image being part of the bigger…
BullyWiiPlaza
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How to make WIX installer adapt to the version of Windows Installer available - like the Hyperlink control

Windows Installer 5 added support for the Hyperlink control which I would like to utilize if available. I cannot set a dependency towards Windows Installer 5 (doesn't support WinXP), but I would like my installer to be able to utilize the hyperlink…
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How to use feature detection to know if browser supports css hover?

How can I use feature detection to determine whether a browser supports the :hover pseudo class? I want to do this WITHOUT using conditional comments to include ie6-specific script files if possible.
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OpenCV Error: Bad argument (bytes must be 16, 32, or 64) in BriefDescriptorExtractorImpl

I am trying to detect feature points using SURF and descriptor extractor using BRIEF. cv::Ptr detector = xfeatures2d::SurfFeatureDetector::create(400); Mat descriptors_img1, descriptors_img2; //-- Step 2: Calculate descriptors (feature…
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CSS feature detection with styled-components

I typically use Modernizr to feature-detect for CSS features like flex-box support and fall back to older methods if unsupported: .mz-flexbox { // use flex } .mz-noflexbox { // use floats } How would one accomplish something similar with…
typeoneerror
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