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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Detect different kinds of circles and ovals on the image using OpenCV and Python

I need to detect the different shapes on the image such as ellipses and circles with a dashed-border. Using OpenCV causes some troubles, for e.g. openCV detects not a contour but an amount of small separated lines(contours). In case of ellipse with…
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Feature detection with opencv fails with seg fault

I have the following code cv::initModule_nonfree(); std::vector keypoints_1; cv::Ptr detector = cv::FeatureDetector::create("SURF"); cv::Mat image = cv::imread("someFileNameHere",cv::IMREAD_COLOR); // image.data is…
Alexandru Barbarosie
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Opencv Python - Similarity score from Feature matching + Homograpy

I have several fish images in my database , My Goal is to find similarity score between user input fish image and images in database. For that I am using opencv Feature matching + Homograpy from this…
Pawan
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Understanding encoding of extracted features

The encoding I am focusing on is fisher encoding as i has shown to have best results with my work. So I want to test fisher encoding on my extracted (SIFT) features and test the performance of the system with or without encoding. Rather than…
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Difference between Low-Level and High-Level Feature Detection/ Extraction

According to this Wikipedia article Feature Extraction examples for Low-Level algorithms are Edge Detection, Corner Detection etc. But what are High-Level algorithms? I only found this quote from the Wikipedia article Feature Detection (computer…
ironmouse
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Opencv Repeatability Result not make sense?

i'm trying to evaluate SIFT and SURF Detectors by Repeatability criteria. i find out that below method can find Repeatability ,Correspondence of SIFT and SURF cv::evaluateFeatureDetector(img_1c, img_2c, h12, &key_points_1, &key_points_2,…
Alireza
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Why do SURF feature points have floating point coordinates?

I have just written the C++ OpenCV 2.4.7 code to extract feature points in stereo images using SurfFeatureDetector. It worked well but I got confused when I realized that the point coordinates are floating points, say for example it found…
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Feature detector and descriptor for low resolution images

I am working with low resolution (VGA) and jpg-compressed sequences of images for visual navigation on a mobile robot. At the moment I am using SURF for detecting keypoints and extracting descriptors out of the images, and FLANN for tracking them. I…
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Extract one object from bunch of objects and detect edges

For my college project I need to identify a species of a plant from plant leaf shape by detecting edges of a leaf. (I use OpenCV 2.4.9 and C++), but the source image has taken in the real environment of the plant and has more than one leaf. See the…
Grant
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How can I find the largest quadrangle

How can I find the largest quadrangle in this case? In the attached image you can see what I have (in the left) and what I wantto get (in the rigth). This code won't work because the largest rectangle has crosses instead of corners. int…
Rougher
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What is a good algorithm or library for cropping images to avoid whitespace or empty areas?

I have a whole bunch of images of illustrations that I would like to crop to a smaller preview size. The problem is that I want to crop them to show an "interesting" part of the illustration (ie avoid areas of whitespace). The images typically have…
user139107
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Draw matched points between two images in MATLAB

I am working on a fingerprint recognition system and have completed the step in feature extraction. I have two sets of matching points between two images. What I want to do is create an image so that the two images are displayed side by side. This…
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drawing a line between feature points without using "drawmatches" function

I got the feature points from two consecutive by using different detectors in features2d framework: In the first frame, the feature points are plotted in red In the next frame, the feature points are plotted in blue I want to draw a line between…
sy456
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Different results for Fundamental Matrix in Matlab

I am implementing stereo matching and as preprocessing I am trying to rectify images without camera calibration. I am using surf detector to detect and match features on images and try to align them. After I find all matches, I remove all that…
Martin Ch
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metrics for feature detection/extraction methods

I wonder how do we evaluate feature detection/extraction methods (SIFT,SURF,MSER...) for object detection and tracking like pedestrians, lane vehicles etc.. Are there standard metrics for comparison? I have read blogs like…
sy456
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