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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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Android - Face feature detection

Currently I'm working on an app for Android phones. We want to detect features of a face. The programm should be able to detect the positions of the eyes, the nose, the mouth and the edge of the face. Accuracy should be fine but doesn't need to be…
tschoartschi
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How to train and predict using bag of words?

I have a folder of images of a car from every angle. I want to use the bag of words approach to train the system in recognizing the car. Once the training is done, I want that if an image of that car is given it should be able to recognize it. I…
ipunished
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How to build a custom opencv.js with opencv_contrib

I would like to include xfeatures2D from opencv_contrib into opencv.js. I follow this documentation Build OpenCV.js. Everything is ok. I got a brand new opencv.js that I'm able to use in my html page, but it doesn't include the xfeatures2D module. I…
Laurent Trillaud
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Implementing a Harris corner detector

I am implementing a Harris corner detector for educational purposes but I'm stuck at the harris response part. Basically, what I am doing, is: Compute image intensity gradients in x- and y-direction Blur output of (1) Compute Harris response over…
Etan
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opencv 3, blobdetection, The function/feature is not implemented () in detectAndCompute

I have a problem with opencv 3: I want to use a feature detector, SimpleBlobDetector, about to use filters by convexity and circularity. But when I try to execute the code, the following error is tracked: The function/feature is not implemented ()…
Vincent Lartaud
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How to find the corners of a Rect object in openCV?

I am using openCV library on the android platform. I have successfully detected the largest rectangle from the image but since my application will be used for the scanning purpose ,i want to have the perspective change functionality as well. I…
Ankur Gautam
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OpenCV HOGDescriptor Errors

I am running OpenCV 2.4.3 on Mac OS X 10.8. I am trying to use the cv::HOGDescriptor to get pedestrians in a video sequence. This is the code I am using to do the detection and paint a bounding box. cv::VideoCapture input("file.avi"); …
ssb
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OpenCV: Detect blinking lights in a video feed

I have a video feed. This video feed contains several lights blinking at different rates. All lights are the same color (they are all infrared LEDs). How can I detect the position and frequency of these blinking lights? Disclaimer: I am extremely…
Adam Paynter
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Feature detection when P/Invoking in C# and .NET

i'm trying to find a good way to detect if a feature exists before P/Invoking. For example calling the native StrCmpLogicalW function: [SuppressUnmanagedCodeSecurity] internal static class SafeNativeMethods { [DllImport("shlwapi.dll", CharSet =…
Ian Boyd
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Memory-efficient line stitching in very large images

Background I work with very large datasets from Synthetic Aperture Radar satellites. These can be thought of as high dynamic range greyscale images of the order of 10k pixels on a side. Recently, I've been developing applications of a single-scale…
Peter T.B. Brett
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Feature detection with patent-free descriptors

I need the feature detection algorithm. I'm fed up surfing on the web finding nothing but SURF example and hints how to do that, but I did not find an example with other than patented descriptors like SIFT or SURF. Can anybody write an example of…
denis631
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What the Hessian minimum threshold means on the SurfFeatureDetector function?

I'm working on a OpenCV project using surf to detect feature from images. The detector is initialized in this way int minHessian = 100; SurfFeatureDetector detector( minHessian ); Can someone explain me the meaning of the hessian threshold (in a…
Fabrizio Duroni
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How to Handle Occlusion and Fragmentation

I am trying to implement a people counting system using computer vision for uni project. Currently, my method is: Background subtraction using MOG2 Morphological filter to remove noise Track blob Count blob passing a specified region (a line) The…
bonchenko
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Create Feature detection for One Javascript Feature (intersectionObserver)

Is there a way of storing a built-in javascript method in a variable to set different behaviour for when this method isn't available in certain browsers? My specific case is for intersectionObserver which isn't available in Safari or older MS…
pjk_ok
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Object detection with OpenCV SVM

I was unable to find good explanations at one place on the internet. There are too much stuff and instead of finding out what to do, I get more confused. My goal: Create an Android application that detects objects in real time using the camera (my…
dephinera
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