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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Cannot perform corner matching between two images

I'm using openCV 2.4, where I'm using FlannBasedMatcher to match keypoints. However, instead of using SurfFeatureDetector::detect()to extract keypoints, I'm passing the image corners as keypoints. Sadly I'm getting zero matches for all values of…
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OpenCv: Feature matching, match descriptors to knn filtered keypoints?

I have the following code, which I use to detect and match Keypoints detected in two images. I detect the keypoints, and store the descriptors in these: cv::Mat descCurrent; cv::Mat descCurrentR; Then pass them to this…
anti
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Returning a value of match in images from feature point detection

I'm using a feature point detection algorithm I found in a tutorial as shown below. The output of this code are lines drawn between the two images where feature points match. Here's what I would like to know: Is there a way to return some value…
akrama81
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Getting error using drawMatches for feature point detection in OpenCv 2.4.13.2 for Python

I'm trying to use the Feature Point Matching tutorial found here: http://opencv-python-tutroals.readthedocs.io/en/latest/py_tutorials/py_feature2d/py_feature_homography/py_feature_homography.html But, I'm getting undefined error on drawMatches: img3…
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Features matching OpenCV

I am using this code for matching features on two images. The output is not that accurate, have lots of positive negatives. How is it possible to increase the accuracy overall? output Main Image import numpy as np import cv2 from…
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How does openCVs ORB achieve scale invariance?

After scrolling through the openCVs ORB implementation https://github.com/opencv/opencv/blob/master/modules/features2d/src/orb.cpp and reading the original paper: ORB achieves scale invariance by a scale pyramid, to quote the paper: " We employ a…
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Error with pca and randomized lasso

There are two .csv files containing Tweets and a classification for each Tweet: pos, neg and neutral. class means classification and text a Tweet. This is my code: def prediction(): print("Reading files...") #Will learn from this data set. …
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Detecting sub-optimal objects and separate them from edges if necessary

I've been puzzled with this problem for quite a lot time. I went through a lot of topics and didn't find out exactly what I need. So I started this question. This is the test image I need to extract features from: And The final product I want to…
TJ2017
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OpenCV, Android, Android-Studio: Detecting Object from video URI

I'm pretty new to android app development, and I'm currently working on a school project that requires my application to capture a video using my android phone and then detect an object in this case the object is a AA battery, using openCV, in the…
Tix
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Object Detection for 2-D Shapes using Feature Detection?

My objective - Input: A PNG floorplan (with many electrical equipment symbols on it), and a user who selects one of those symbols using a bounding box. Output: The same PNG floorplan but with all matching symbols highlighted I have been looking…
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Detect laser light dot of any colour using OpenCV in Android

I am trying to detect laser light dot of any colour of laser.and i have done some reference code from here OpenCV Android Track laser dot That code is running perfectly for Only RED colour detection and i want any colour of laser dot detection. I am…
Vishal Thakkar
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Different ways of detecting smile

I would like to know more about different ways of detecting smile on image. As far as I know, there are many libraries that are allowing to detect face and smile. The ones that I've tried are: FaceSDK from Luxand OpenCV OpenIMAJ Instead of just…
deem
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Sift vs Surf. Which is more accurate?

I am testing object to do Feature Matching with Sift and Surf with C++ & OpenCV. Surf claims to be faster and Sift claims can detect many keypoints than Surf. I want to determine which algorithm is the most accurate. But I am confused to determine…
Command14
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How To Falsely Report Browser Features as existing or not existing

This site (https://html5test.com/index.html) can be used to list browser features upon visiting. I'm using ElectronJS (Chromium-based) and I'd like to have control over the features that get reported to feature detection mechanisms. I can do…
xendi
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Remove de-focus region on image by opencv

I have an image and 2 regions (focus region and de-focus region). I use Open CV, I want to detect near region. I apply watershed in OpenCV or Canny detector to detect the object. But the object includes near and far region. So, I need an idea or…
trongan93
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