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
4
votes
2 answers

Object detection with OpenCV Feature Matching with a threshold/similarity score - Java/C++

I am in the process of creating a small program which detects objects(small image) in the large image and I am using OpenCV java. As I have to consider rotation and scaling I have used FeatureDetector.BRISK and DescriptorExtractor.BRISK. Following…
4
votes
1 answer

Using FeatureDetector in OpenCV gives access violation

I need to find and match feature points in stereo images. Therefore I want to compare the different Feature Detection algorithms that are supported in OpenCV 2.4.5. by passing "SURF", "SIFT", etc. to the function. The code snippet: #include…
filla2003
  • 724
  • 1
  • 8
  • 18
4
votes
2 answers

active appearance model (AAM) vs active shape model (ASM)

I was googling the last few days about active appearance model (AAM). I found a shape model and texture model and now I'm trying to do some research about active shape model (ASM) and I'm getting confused. Are the active shape model (ASM) and the…
TIBOU
  • 337
  • 2
  • 6
  • 16
4
votes
1 answer

jquery maskedinput. How to check availability of the mask

Can anyone help me with checking availability of the mask. I use this one: if ($.isFunction($("#ID").mask)){ var val = $("#ID").mask(); } else { var val = document.getElementById(ID).value; } but this condition is always TRUE. Don't matter…
4
votes
1 answer

How can I feature test a browser's ability to use video as a canvas source

As some of you might know it's not possible to use HTML5 video as an image source for canvas elements on mobile devices (the video will be opened in an external player instead of the browser). I need a feature test for that. As I cannot simply check…
m90
  • 11,434
  • 13
  • 62
  • 112
4
votes
2 answers

Feature flags best practice: condition inside or outside of a method?

We're using feature flags in order to enable/disable certain features in our system. I had a discussion with my colleague over what's the standard way of adding feature flags to the code itself: Consider the following method: def featured_method …
Mikey S.
  • 3,301
  • 6
  • 36
  • 55
4
votes
2 answers

Access violation reading in FeatureDetector OpenCV 2.4.5

I tried the sample codes about matching to many images in OpenCV 2.4.5 and I modified that code. I found the error code: Unhandled exception at 0x585a7090 in testing.exe: 0xC0000005: Access violation reading location 0x00000000. Its fault is at…
Dominikus Willy
  • 127
  • 3
  • 8
4
votes
1 answer

OpenCV descriptor removes keypoint

OpenCV 2.4 has detector and descriptor. I am creating keypoints for a lot of images and the problem is that the detector gets the keypoints but the descriptor sometimes removes them all. How do I disable the descriptor from removing the points? Is…
4
votes
1 answer

How to make my own feature detection method in opencv?

Let's take a look on this basic tutorial named Features2D + Homography to find a known object. It uses SurfFeatureDetector to detect features: SurfFeatureDetector detector( minHessian ); std::vector keypoints_object, keypoints_scene; …
fen1ksss
  • 1,100
  • 5
  • 21
  • 44
4
votes
1 answer

Improving the result of harris corner detector

Ive been reading about feature detection and wanted to try harris corner detector. I realize that it is achieved by calling void cornerHarris(InputArray src, OutputArray dst, int blockSize, int ksize, double k, int borderType=BORDER_DEFAULT ) where…
StuckInPhDNoMore
  • 2,507
  • 4
  • 41
  • 73
4
votes
2 answers

Feature detection of foreignObject in SVG

I am using the foreignObject element in SVG, however IE9 does not support this element. I am looking at a way the detect this feature. Modernizr does not detect this feature and it seems I can not use createSVGForeignObject (not available on…
3
votes
2 answers

Javacv Blob detection

I would like to use some blob detection in my application which is written in Java and thus using JavaCV instead of OpenCV. I found many classes like: SimpleBlobDetector, CvBlobDetector, CvBlob, ... but I can't find any tutorial or demo/example code…
hhoud
  • 518
  • 2
  • 6
  • 18
3
votes
1 answer

SurfDescriptorExtractor/featureDetector - OpenCv in IOS

i am working on an iphone project which uses openCV for some image matching. Initially I was using cvMatchTemplate(), but the output is not what we expected. so I am now trying to implement SURF detector using FLANN. I tried to port the following…
Nandakumar R
  • 1,404
  • 11
  • 17
3
votes
2 answers

How does HOG feature descriptor training work?

There doesn't seem to be any implementations of HOG training in openCV and little sources about how HOG training works. From what I gathered, HOG training can be done in real time. But what are the requirements of training? How does the training…
mugetsu
  • 4,228
  • 9
  • 50
  • 79
3
votes
0 answers

OpenCV Good Features to Track how to set quality measure?

The Shi-Tomasi Corner Detector in python OpenCV looks like this: feature_params = dict(maxCorners=100, qualityLevel=0.3, minDistance=7, blockSize=7) p0 = cv2.goodFeaturesToTrack(frame, mask=None, **feature_params) The documentation says that…