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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OpenCV coin detection and automated results checking

I am working on a project of coin identification. First thing I with that I am stuck is correct coin extraction from the image, even from very simple image. There are exists alot of good working methods for coin detection but all of them as I see…
Oleg
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OpenCV 3.0.0 SurfFeatureDetector and SurfDescriptorExtractor Errors

I am attempting to implement the OpenCV 3.0.0 SURF Feature Description and Detection but after running the sample code on the OpenCV site, I receive a load of errors all related to SURF. Any idea of what could be going wrong? Thanks! #include…
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ORB giving better feature matching than SIFT - why?

I have rencently been trying to solve a problem using feature matching, utilizing the feature matching algorithms provided by the OpenCV libraries in C++. Now there is one example where ORB gives me better matches than SIFT, what made me wonder. I…
bweber
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OpenCV logo detection - What to use?

I want to create an Android application for logo detection. I want to ask you which approach would be better: Using feature detector and extractor and then findHomography(); 1.1 Which detector/extractor should I use? Is it necessary to use SURF …
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OpenCV - match SURF points runtime error

I have a program which matches feature points found in a template image to those shown in the video feed. When I run the program I am getting the following error: OpenCV Error: Assertion failed (i1 >= 0 && i1 < static_cast(keypoints1.size()))…
Colin747
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OpenCV FAST - too many features

I'm trying to extract features so I can later train a SVM which will be used in Android app. I'm using python to find and extract the features because it is easy to write and saves time. My problem is that I get too many features and I don't know…
dephinera
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Detecting support for beginElement()

I'm using beginElement() to start an SVG animation in my web app: document.getElementById("item").beginElement(); But this causes the following error in IE9 and up (which doesn't support it): Object doesn't support property or method…
daGUY
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OpenCV: When to use GridAdaptedFeatureDetector?

I am trying to make a detector based on descriptors. I am using OpenCV and I have seen that there are many feature types and descriptor types, and also matcher types. More I have also seen that there can be composed types like Grid or Pyramid for…
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Tracking in video sequence with user-defined target to track

I have a project to create an application where the user can draw of region of interest (in this example, a rectangle around a vehicle to track) and it will automatically track the vehicle in the subsequent frames of the recorded video. The method I…
salgarcia
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How to find multiple instances of my training image with OpenCV and SIFT

So far I've been able to detect key points from my training image within my query image very accurately using BFMatcher. However, I have dozens of instance of my training image (a bee) occurring within my query image (the frame of a beehive). Is it…
Jack Simpson
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GPU based SIFT feature extractor for iOS?

I've been playing with the excellent GPUImage library, which implements several feature detectors: Harris, FAST, ShiTomas, Noble. However none of those implementations help with the feature extraction and matching part. They simply output a set of…
Rob
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Filled circle detection using CV2 in Python?

I am trying to detect all the circles in images like this. I have many different images like this but in all the circles will be black (or almost black) and of the same size (+/- a couple of pixels). I believe there are exactly 2943 circles in each…
user2991438
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OpenCV: Drawing matches in top and bottom configuration?

I am trying to use drawmatches function in OpenCV. It put the image in left and right format. I want the images to be put in top-down format and then draw the matches for more clarity. Is there a way in which it can be done in OpenCV? Or, I will…
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Which feature detector algorithm is simplest for learning?

I am wrapping my head around feature detector algorithms. I've studied the options that I have: SIFT, SURF, BRISK, FREAK etc. All of them seem fairly complex in terms of underlying mathematics. On the contrary, I want to take one step at a time…
c0dehunter
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cv::SimpleBlobDetector detect() produce access violation exception in Visual Studio 2010

First some background I have written a C++ function that detect an area of a certain color in an RGB image using OpenCV. The function is used to isolate a small colored area using the FeatureDetector: SimpleBlobDetector. The problem I have is that…
Dyrborg
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