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
0
votes
0 answers

using OpenCV Matches

I'm confused about what OpenCV (feature2D) Matches are, i'm using OpenCVSharp and doing something like: var pt1 = detector.Detect(img1); var pt2 = detector.Detect(img2); Mat desc1 = new Mat(); …
Ronan Thibaudau
  • 3,413
  • 3
  • 29
  • 78
0
votes
0 answers

Get good approximated segmentation mask within the detection rectangle

I want to get a fast and good approximated segmentation of my object within its detection box. How could I do that? I tried background subtraction algorithms and grab cut but they dont look that promising.
0
votes
1 answer

Distance between same point in two different images not consistent - OpenCV/C++

So I have two Thermal images (Potato quality I know but it is what I have to work with), the first two images in this album. I am using some code from a tutorial that is super common but have edited a lot of…
Jay Bell
  • 447
  • 7
  • 20
0
votes
1 answer

blob detection in unity3d: NullReferenceException

I am new to C#. I am trying to do blob detection using opencv asset in unity3d. I am getting this error: NullReferenceException: Object reference not set to an instance of an object after line 89 (where I call detector.detect) The unity console…
ypag
  • 1
  • 2
0
votes
0 answers

Feature Tracking by using Lucas Kanade algorithm

Lucas Kanade Feature Tracker Refer Page 6 I am implementing the Lucas Kanade Feature Tracker in C++. One thing is unclear in implementing the equation 23 which is mentioned in attached paper. I think Matrix G…
0
votes
1 answer

How to separate the query and the train image from the Mat object returned from DrawMatches() method

I am trying to detect an object in a video. i am using SURF as feature detection and descriptor extractor, and BRUTFORCE as matcher. i tested my work with faces, i captured a picture of me and when i run the camera and direct it toward me, my face…
0
votes
1 answer

Comic Balloon Detection: How can I count white pixels inside a vector Ellipse in OpenCV?

I've been looking everywhere I can for the answer but I can't find one. I'm making a comic balloon detection program and I need to find an ellipse that have a specific percentage of white inside the contour (percentage is to be decided later), thus…
0
votes
0 answers

how can I extract pores from an input binary fingerprint image using marker control watershed segmentation in MATLAB

I am working on pore extraction from binary fingerprint image, On using the watershed segmentation, I managed to get the gradient image but now I want to extract the pores(white blobs) from the ridges(the lines across the fingerprint).How do I go…
0
votes
2 answers

CSS feature detection using media queries

I'm trying to detect if the browser supports the transform property. To do so I'm wrapping the code I want to apply when the transform is supported inside a media query: @media (transform: none) { // My code } With this code, this part is not…
Fez Vrasta
  • 14,110
  • 21
  • 98
  • 160
0
votes
1 answer

Detecting Elliptical patterns in image

In this image there are some lines and some elliptical (circular) patterns on these lines. I want to detect these elliptical patterns in C# using Emgu.CV and OpenCV functions. Can any body please help me where should I start and what should I do…
0
votes
0 answers

Is there any way to execute image processing functions (such as image transforms, feature matching, etc) using raspberry?

I am willing to know that is it possible to execute image processing useful techniques such as image transforms, feature extraction, feature matching, etc by raspberry pi? I mean, is this processor powerful enough to perform such computations?
0
votes
1 answer

PCA on Sift desciptors and Fisher Vectors

I was reading this particular paper http://www.robots.ox.ac.uk/~vgg/publications/2011/Chatfield11/chatfield11.pdf and I find the Fisher Vector with GMM vocabulary approach very interesting and I would like to test it myself. However, it is totally…
0
votes
1 answer

OpenCV FeatureDetector is not initialized

I am trying to create a class where I shall find KeyPoints in an image. However, I get a ridiculous error I cannot figure out how to solve. The problem is now that this->detector is zero, so it is for some reason not initialized properly. I have…
El_Loco
  • 1,716
  • 4
  • 20
  • 35
0
votes
1 answer

OpenCV DrawMatchesFlags - no keypoint option?

I am matching the SURF points from an image to a video feed. I am looking to test this at varying resolutions but I'm having the annoying problem that when the matching keypoints are drawn on small resolutions I can no longer see what's happening in…
Colin747
  • 4,955
  • 18
  • 70
  • 118
0
votes
1 answer

Cannot create custom message

Hi i am currently trying to create a custom message for an exisitng package however i create Point_id.msg but when i included it as a header file in my code, i receive the following…
WinnePoon
  • 1
  • 3