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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Feature detect advanced browser multi-select control (e.g. iOS / Android select element)

What's the best way to feature detect whether a user is using a browser that supports advanced multi select controls? For example, multi-select using the native select element on Desktop is terrible, so we've decided to enhance it with select2 (a…
Johnny Oshika
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how to apply mutual information on categorical features

I am using Scikit-learn to train a classification model. I have both discrete and continuous features in my training data. I want to do feature selection using mutual information. The features 1,2 and 3 are discrete. to this end, I try the code…
samira
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Test for IE6 using feature detection instead of user agent testing

I'm using html5boilerplate with the Modernizr library. My application is built using jQuery. Both Modernizr and jQuery have feature detection built in, but my understanding is that Modernizr is more complete. I'm planning to use Modernizr for…
Tauren
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GUI version of OpenCV for feature-detection (SIFT etc.) prototyping before actual project development?

I had an idea for which I need to be able to recognize certain objects or models from a rendered three dimensional digital movie. After limited research, I know now that what I need is called feature detection in the field of Computer Vision. So,…
Tom
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How do I check keypoint matches in opencv (python)?

My question is, how do I check the match rate of the keypoints that are matched through ORB? The code I'm using here is : import numpy as np import cv2 from matplotlib import pyplot as plt MIN_MATCH_COUNT = 10 img1 = cv2.imread('Vegeta4.png',0) img2…
terabaap
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Using inRange() in OpenCV to detect colors in a range

I'm writing a C++ program with OpenCV for lunar crater detection which seems to detect only a small fraction of craters accurately. My strategy for this approach was to first convert the image to HSV, then use inRange() to catch the colors in a…
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Defining a threshold for feature matching in geometrical re-ranking

I'm implementing a cache for virtual reality applications: given an input image query, return the result associated to the most visually similar cached image (so a previously processed query) if the distance between the query representation and the…
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How does keypoint size relate to scale and octave in OpenCV SIFT?

I'm working with SIFT key-points and I need to know the exact relation between the size of the key-point and the scale (and octave?) where it was detected. I came across this size=scale*magnification, however if this is true why are keypoint sizes…
j.teixeira
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Detecting the corners of an incomplete shape with OpenCV in python

I'm working on a program to detect the edges of a shape on a page, and then crop and wrap the image to zoom in on the shape. However, the problem is that my shape is bound by only a marker on each corner. Following is an example image that I am…
agupta231
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How to improve Hough Circle Transform to detect a circle made up of scattered points

I have a very basic code that uses the standardized HoughCircles command in openCV to detect a circle. However, my problem is that my data (images) are generated using an algorithm (for the purpose of data simulation) that plots a point in the range…
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Binary Decriptors in Feature Matching

Dear SO Community Friends, Hope you all welcome me to SO. I just wanted to learn about the feature detectors, descriptors and matchers. I was clear with the detectors and descriptors after my research work and came to know that descriptors are used…
John
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How to detect Multiple occurrences of same objects in an image using Feature detection

Is there any possible way to detect multiple occurrences of same object in an image using feature detection? Earlier I tried it with Template Matching and I was able to detect the multiple occurrences but later I dropped because of its dependency…
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Fracture detection in hand using image proccessing

What I have done : Taken input image and resized image to standard size as I have to compare it with template. converted in binary using threshold value. Detected connected component and displayed largest component. As it is whole hand.as shows…
JYOTI RAJAI
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What is the difference between layers and octaves in SIFT/SURF?

I read both Lowe's papers ('99&'04) and I would say I understood most of them. I saw all SIFT related classes on youtube, but none explicitly says why we would use both octaves and layers? I understood that you get more layers in the same octave by…
Andrei
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How does it work OpenCV Mser for color images?

I am using OpenCV Mser class. For grayscale images I don't have any problems, reults are good and parameters defined in documentation influences to algorithm logically : delta - it compares (sizei−sizei−delta)/sizei−delta min_area - prune the…
Davit
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