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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Transfer selected feature points to a new variable

I'm planning to transfer only a few feature descriptors which have been classified using SVM. I tried to put the selected descriptors in a matrix but I can't match them properly. Here's the code that I made in order to transfer the selected…
Jessie
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feature extraction from websites

this is more of a theoretical question whenever i search the web for feature extracting and feature matching, the only results i get are about image objects.. like finding a face or a patterened pillow etc.. but what im trying to achive is a good…
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Ngram order selection for feature engineering

I am working on feature engineering for text classification. I am stuck at a point over choosing features. Majority of the literatures say tokenize the text and use them as features(remove stop words ,punctuations), but then you miss out on…
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Mixing binary and non-binary features in logistic regression

I have some binary features (0 or 1) and some non-binary features which have values between 0 and 1 (such as 0.24). I use Weka logistic regression to classify instances with all these features. Does it work properly? Thanks
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How to use OpenCL version of SURF?

I use the following code for feature detection: auto detector = cv::xfeatures2d::SURF::create(); std::vector keypoints; for (const cv::Mat& image : images) { detector->detect(image, keypoints); process(keypoints); } Now I try…
Anton3
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Access actual Features after a Feature Selection Pipeline in SciKit-Learn

I use a feature selection in combination with a pipeline in SciKit-Learn. As a feature selection strategy I use SelectKBest. The pipeline is created and executed like this: select = SelectKBest(k=5) clf = SVC(decision_function_shape='ovo') …
beta
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How to do a unicode-range feature detection.

I want to feature detect unicode range. I understand Modernizr has a code for it. Any way to remove the unneeded part from it and simply feature detect?
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How can I segment an object using Kinect V1?

I'm working with SDK 1.8 and I'm getting the depth stream from the Kinect. Now, I want to hold a paper of A4 size in front of the camera and want to get the co-ordinates of the corners of that paper so I can project an image onto it. How can I…
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Error KAZE with opencv: Use of undeclared identifier

I tried to compile a function for extracting the features. Ptr kaze = KAZE::create(); But I get an errors with that. First is "Use of undeclared identifier 'KAZE'" The next line is kaze->detectAndCompute(img, noArray(), keypoints,…
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Android Opencv Why HOG descriptors are always zero?

I am stack with this problem for a couple of days. I want to make an android app that takes a picture and extracts HOG features of that image for future processing. The problem is that the code below always returns the HOG descriptors with rezo…
VassilisCN
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AKAZE not producing good results compared to SIFT in openCV Java

I'm new to the world of computer vision and presently I'm working on a project to compare two images to see if there is a match. I have read that AKAZE performs better compared to SIFT, but I have found otherwise. I'm using the Java implementation…
seriousgeek
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Find logo in image

I'm trying to write a C++ programme to look for given images (logos) in pictures, and I've used code from here: http://docs.opencv.org/2.4/doc/tutorials/features2d/feature_homography/feature_homography.html So, I have two images - one is a logo, and…
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feature matching/detection on brain images

This question is for those who have tried feature detection/matching methods on brain images - it is a broad one, and perhaps a bad one: How could you tell if the method you used was "good enough?" What does a successful matching/detection test look…
haxtar
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Why Sift Feature Detector cannot detect key points for some images?

I am reading images from a set and extracting their features. However, for some images(very few, around 4 per mille), SiftFeatureDetector::detect( image, keypoints) cannot detect key points and returns me an empty set of key points. When I tried…
Aka
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In OpenCV, what does descriptorType() of DescriptorExtractor class return?

I detected key points and extracted the features. vector > key_points; SiftFeatureDetector feature_detector; feature_detector.detect( db_images_gray, key_points); Ptr descriptor_extractor =…
Aka
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