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.

909 questions
9
votes
3 answers

OpenCV filtering ORB matches

I am using the ORB feature detector to find matches between two images using this code: FeatureDetector detector = FeatureDetector.create(FeatureDetector.ORB); DescriptorExtractor descriptor =…
Stefan Manciu
  • 490
  • 1
  • 6
  • 19
9
votes
3 answers

OpenCV: howto use mask parameter for feature point detection (SURF)

I want to limit a SurfFeatureDetector to a set of regions (mask). For a test I define only a single mask: Mat srcImage; //RGB source image Mat mask = Mat::zeros(srcImage.size(), srcImage.type()); Mat roi(mask, cv::Rect(10,10,100,100)); roi =…
Hyndrix
  • 4,282
  • 7
  • 41
  • 82
9
votes
1 answer

opencv - object tracking using feature detection

I want to track an object(for example, a moving ball) in a video. Referring to opencv tutorial - 'Features2D + Homography to find a known object', I have been able to track my object in a still image by providing a reference image. I plan to use a…
PJ_123
  • 93
  • 1
  • 3
8
votes
3 answers

Feature detection for position: fixed

I am trying to find a script that detects if a device places position: fixed elements relative to the ViewPort and not to the entire document. Currently, standard desktop browsers and Mobile Safari (for iOS 5) do so, whereas Android devices place…
pau.moreno
  • 4,407
  • 3
  • 35
  • 37
8
votes
7 answers

How to feature-detect whether a browser supports dynamic ES6 module loading?

Background The JavaScript ES6 specification supports module imports aka ES6 modules. The static imports are quite obvious to use and do already have quite a good browser support, but dynamic import is still lacking behind. So it is reasonably…
rugk
  • 4,755
  • 2
  • 28
  • 55
8
votes
2 answers

EmguCV (OpenCV) ORBDetector finding only bad matches

Problem So I am fairly new to Computer Vision in general. I am currently trying to calculate a homography by analyzing 2 images. I want to use the homography to correct the perspective of 1 image to match the other. But the matches I am getting are…
Robin B
  • 1,066
  • 1
  • 14
  • 32
8
votes
3 answers

Feature-detect: mutation-event availability in JavaScript?

How can my JavaScript detect if an event is available? I'm aware of some great event-compatibility tables, but I need to use feature detection, not browser-sniffing plus a lookup table. Specifically, my JS makes great use of the DOM mutation…
8
votes
1 answer

Feature detect if user gesture is needed

is there a way to detect if calling play() on a video element is allowed without a user gesture? On Android Chrome this warning is given: Failed to execute 'play' on 'HTMLMediaElement': API can only be initiated by a user gesture. So on Chrome…
oskbor
  • 1,592
  • 18
  • 35
8
votes
1 answer

Detecting Circle Using Hough Transform

I'm trying to detect circles with using hough transform. With my current code I can detect the one below But I want to find black hole inside the circle I've detected. however changing parameters of houghcircle method is not helped me. Actually…
8
votes
2 answers

Are there any detectors which implemented on GPU and are scale/rotate-invariant?

As known in OpenCV 2.4.9.0 are these feature-detectors: SIFT, SURF, BRISK, FREAK, STAR, FAST, ORB.…
Alex
  • 12,578
  • 15
  • 99
  • 195
8
votes
1 answer

How to detect if a compiler supports static_assert?

I want to detect, in source file, if the compiler used supports static_assert.
nialv7
  • 223
  • 3
  • 9
8
votes
2 answers

feature detectors and descriptors comparison

There are several kinds of detectors and descriptors, like SIFT, SURF, FAST. I wonder are they all eligible for real-time applications? Which is the best or better? And furthermore, is Harris-Laplacian dectector still useful when we already have the…
Alcott
  • 17,905
  • 32
  • 116
  • 173
8
votes
3 answers

Saving ORB feature vectors using OpenCV4Android (java API)

I have a training set of images, for each of which I've detected and computed their feature vectors (using ORB feature descriptors and extractors. The questions is: since I need to save those features to reutilise them for matching against test…
Noha Kareem
  • 1,748
  • 1
  • 22
  • 32
7
votes
1 answer

matlab extract features in matfile

I have images of 30 different leaves in white background numbered 1-30. I'm working on a project in image processing where the user can load a new leaf image with white background and the program will compare it with the images on the database and…
Mary Ann
  • 133
  • 1
  • 10
7
votes
0 answers

Meaning of algorithm, trees, and checks during Flann based feature matching (OpenCV, python)

I am currently testing Flann feature matching with OpenCV in python, and do not fully understand what some of the parameters actually do. Here is a snippet of code copied from the OpenCV docs. The full code can be found here. # FLANN…