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 for web/ javascript

I have to use OpenCV in a web application. I know the Python and the C++ library but I need to use it with Express.js now. For this I need object detection, feature detection, preferably SIFT and eventually basic stuff from the machine learning…
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OpenCV, Python: How to stitch two images of different sizes and transparent backgrounds

I've been working on a project where I stitch together images from a drone flying in a lawn mower pattern. I am able to stitch together images from a single pass (thanks to many answers on stackoverflow) but when I try to stitch two separate passes…
Victor Odouard
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It is really necessary to use Modernizr?

Especially if as JS feature detection can i use: if (localStorage in window) { // you have local storage } or even easier: if (crypto.subtle) { // you can encrypt document} And for css detection: if (CSS.supports('display', 'flex')) { // you can…
user6748331
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Skin Color Detection

I am using the following algorithm to detect skin color, but its not working real well in different lighting conditions. Can anybody offer any advice how to improve it or suggest a better approach R > 95 AND G > 40 AND B > 20 AND max{R, G, B} –…
user346443
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Understanding a FastICA implementation

I'm trying to implement FastICA (independent component analysis) for blind signal separation of images, but first I thought I'd take a look at some examples from Github that produce good results. I'm trying to compare the main loop from the…
Austin
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Detecting weak blobs in a noise image

I have an image which may contain some blobs. The blobs can be any size, and some will yield a very strong signal, while others are very weak. In this question I will focus on the weak ones because they are the difficult ones to detect. Here is an…
Markus
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Detect if browser supports local mDNS querying

It appears that some browsers support querying for local mDNS addresses (of the type http://hostname.local/), while others don't. It looks like iOS supports this in it's networking stack itself, so all browsers on iOS support .local addresses. On…
Rakesh Pai
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Feature tracking not working correctly on low Resolution images

I am using SIFT for feature detection and calcOpticalFlowPyrLK for feature tracking in images. I am working on low resolution images (590x375 after cropping) taken from Microsoft kinect. // feature detection cv::Ptr detector =…
Ruturaj
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Image Recognition Techniques for Identifying Logos (Brands)

I started learning Image Recognition a few days back and I would like to do a project in which it need to identify different brand logos in Android. For Ex: If I take a picture of Nike logo in an Android device then it needs to display "Nike". Low…
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Feature Detection Algorithms and Feature Descriptor Algorithms

I came to know about the difference between a detector and descriptor from the posts of SO. I would like to know the common word which represents both the feature detection algorithms and feature descriptor algorithms. Is there any word for…
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OpenCV Feature matching to check similarity between two scenes

I am working on a project and I have to make an AR drone follow a path based on a list of checkpoints which are saved in a directory. Each checkpoint is a scene that the drone should detect along its path. There could be differences between the…
leoxama
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DLIB : Training Shape_predictor for 194 landmarks (helen dataset)

I am training DLIB's shape_predictor for 194 face landmarks using helen dataset which is used to detect face landmarks through face_landmark_detection_ex.cpp of dlib library. Now it gave me an sp.dat binary file of around 45 MB which is less…
NAYA
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setting blob detection parameters in python

I am running blob detection on a camera image of circular objects, using OpenCV 2.4.9. I run a number of standard filters on the image (blur, adaptive threshold, skeletonization using skimage routines, and dilation of the skeleton), and would like…
eudoxos
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how to improve orb feature matching?

I am trying to register two binary images. I used opencv orb detector and matcher to generate and match feature points. However, the matching result looks bad. Can anybody tell me why and how to improve? Thanks. Here are the images and matching…
fnhdx
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Feature extraction of 3D image dataset

Assume a workflow for 2D image feature extraction by using SIFT, SURF, or MSER methods followed by bag-of-words/features encoded and subsequently used to train classifiers. I was wondering if there is an analogous approach for 3D datasets, for…