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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can HOG feature detection be used to keypoint matching?

I see HOG is often used with SVM for target detection, can it be used in matching keypoints in two images? and btw, where could I find OpenCV sample of using HOGDescriptor?
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Modernizr checks that exclude IE6, IE7, IE8 or IE at all, that identify iOS devices

Are there any checks (or combinations of checks) I can run with Modernizr where: IE6 fails, but higher versions do not fail? IE7 fails, but higher versions do not fail? IE8 fails, but higher versions do not fail? all IEs fail? all browsers fail,…
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How to use feature detection to know if browser supports border-radius? (Including IE9)

I've seen plenty of examples for detecting support for border radius using something like: var cssAttributeNames = ['BorderRadius', 'MozBorderRadius', 'WebkitBorderRadius', 'OBorderRadius', 'KhtmlBorderRadius']; for (var i = 0; i <…
mhildreth
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Detect ES6 import compatibility

I understand that you can detect features in javascript with something like this if(xmlhttprequest){ console.log("this browser is ajax compatible"); } I also understand that ES6 imports are nativly compatable with some browsers if certain dev mode…
megaman
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Measure of image similarity for feature matching?

I'm currently trying to work with a Brute Force feature matcher using SIFT in openCV, using python. I'm trying to utilise it for my image search function on my server, where I'm inputting an image and having that image be compared with others, in…
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Laser light detection with OpenCV and C++

I want to track a laser light dot(which is on a wall) with a webcam and i am using openCV to do this task. can anybody suggest me a way to do it with C++. Thank you !
Keshan
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Proper approach to feature detection with opencv

My goal is to find known logos in static image and videos. I want to achieve that by using feature detection with KAZE or AKAZE and RanSac. I am aiming for a similar result to: https://www.youtube.com/watch?v=nzrqH... While experimenting with the…
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What is the difference between phase correlation and template matching in OpenCV?

I recently discovered phase correlation in OpenCV, which with the Log Polar Transform (LPT) can perform rotation and scale invariant template matching. I'm wondering what the difference is between this method and all the template matching methods…
nickponline
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Template Matching for Coins with OpenCV

I am undertaking a project that will automatically count values of coins from an input image. So far I have segmented the coins using some pre-processing with edge detection and using the Hough-Transform. My question is how do I proceed from here? I…
Leo
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Warp perspective and stitch/overlap images (C++)

I am detecting and matching features of a pair of images, using a typical detector-descriptor-matcher combination and then findHomography to produce a transformation matrix. After this, I want the two images to be overlapped (the second one…
user4688547
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OpenCV python error when using ORB images feature matching

I was trying to match two images using OpenCV ORB as explained in this tutorial. Here is my code: import numpy as np import cv2 import six import pyparsing import dateutil from matplotlib import pyplot as plt import timeit import os import…
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Group detection in data sets

Assume a group of data points, such as one plotted here (this graph isn't specific to my problem, but just used as a suitable example): Inspecting the scatter graph visually, it's fairly obvious the data points form two 'groups', with some random…
Sami
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FeatureDetector vs. FeatureFinder in OpenCV

I'm trying to understand the difference between the FeatureDetector class and the FeatureFinder class. I've seen panorama examples written in OpenCV use both of these classes and it appears to be possible to use the SURF algorithm with either one.…
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feature detect incorrect overflow with border-radius

As we know does overflow: hidden in combination with border-radius not work in all browser as it should — namely Safari and Opera have problems cutting the rounded corners off contained images. Example HTML:
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The Harris & Stephens corner detection algorithm: determinant always 0 (zero)

As part of my Bachelor-Thesis, I'm trying to implement a corner detector with the Harris and Stephens algorithm: A combined Corner and Edge Detector I do calculate: The x- and y- deviations with sobel Filters (3x3) Calculate the system Matrix M M =…
muuh
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