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Questions tagged [opencv]

OpenCV (Open Source Computer Vision) is a library for real time computer vision. When using this tag, please add a language specific tag (python, c++, ...), if relevant.

OpenCV is a code library for Computer Vision related applications, spanning from many very basic tasks (capture and pre-processing of image data) to high-level algorithms (feature extraction, motion tracking, machine learning).

It is free software. Versions from 4.5.0 are licensed under the Apache 2 license, versions before that under the BSD 3-clause license. OpenCV provides a rich API in C++, Python, and Java. Third party wrappers are available. The library is platform-independent and often used for real-time image processing and computer vision (e.g. tracking in videos). It supports Windows, Linux, and OS X as well as Android (native and Java) and iOS.

OpenCV was officially launched by Intel in 1999. Version 2.0 (2009) was an important landmark as it introduced the new, comprehensive C++ interface, which since then is also to be used internally in the library. Since this release, OpenCV saw a strong acceleration of development in improving the library and adding new features. Version 3.0, released in 2015, deprecated the C API and emphasized object-oriented design for increased modularity and intuitive interface. More information may be found in Wikipedia.

Latest stable versions:

Homepage: https://opencv.org

Documentation: https://docs.opencv.org

Tutorials including source code:

Books

Note that this list is likely outdated and not vetted for quality. A book or course on computer vision in general, along with the official documentation of OpenCV, will give a better understanding of the matter and the library.

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Books for OpenCV and Python?

Does anyone know if there are any books on OpenCV and Python? I have OReilly Learning OpenCV book but its for C so I'm looking for books/pdfs/online tutorials specifically Python and OpenCV. I've looked at…
user1401950
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Accurate binary image classification

I'm trying to extract letters from a game board for a project. Currently, I can detect the game board, segment it into the individual squares and extract images of every square. The input I'm getting is like this (these are individual letters): At…
Blender
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How do I get a list of webcam devices using opencv?

I am using OpenCV2.2 with videoInput. I want to upgrade to OpenCV2.3.1 where videoInput has apparently been merged into OpenCV2.3. My problem is that there doesn't appear to be a listdevices() function to return all the video sources…
Phil Hannent
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Displacement Map Filter in OpenCV

I'm curious to know how one can implement the effect demonstrated here using OpenCV. I think it's some sort of displacement map filter but I'm not 100% sure. After that page has fully loaded, move the mouse around to see the background image move…
karlphillip
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Drawing and Plotting graph in OpenCV

Does OpenCV provide a function on how to draw and plot a graph? I found this link by Shervin Emami http://www.shervinemami.info/graphs.html which was created by himself.
Mzk
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Key Frame Extraction From Video

I need Need To extract Key Frames from Video/Stream.So is there any standard implementation. I am using open CV. (Currently i am extracting frames each second which is slower i need to improve performance.) So if any one has optimized implementation…
user1178178
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OpenCV Shows Gray Window

I'm trying to display an image using OpenCV. I have the following very basic code: import cv2 img = cv2.imread('myimage.png', 0) # Reads a Gray-scale image img2 = cv2.cvtColor(img, cv2.COLOR_GRAY2BGR) cv2.imshow("window", img2) The window is…
zmbq
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Face Detection with OpenCV for non frontal images

I am trying to use opencv to detect faces. Faces are not frontal, the camera captured the faces from side so only one eye and part of the mouth is viewed. I tried HaarDetectObjects with multiple configurations without getting benefit. I changed the…
Hani
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Python OpenCV SVM implementation

So I have a matrix with my sample images (all turned into vectors) which was run trough PCA/LDA, and a vector which denotes the class each images belongs to. Now I want to use the OpenCV SVM class to train my SVM (I am using Python, OpenCV 2.3.1).…
Veles
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Supervised Motion Detection Library

Can anyone recommend a motion detection library that's trainable via a supervised learning algorithm? I have an IP webcam that I'm trying to detect motion from. I'm been using the motion software detector project to do this, but I'm getting a lot of…
Cerin
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Difference between adaptive thresholding and normal thresholding in opencv

I have this gray video stream: The histogram of this image: The thresholded image by : threshold( image, image, 150, 255, CV_THRESH_BINARY ); i get : Which i expect. When i do adaptive thresholding with : adaptiveThreshold(image,…
Olivier_s_j
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track eye pupil in a video

I am working on a project aimed to track eye pupil. For this I have made a head-mounted system that captures the images of the eye. Completed with the hardware portion I am struck in software part. I am using opencv. Please let me know what would be…
siso
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Head pose estimation with Opencv

I am using OpenCV Haar Algorithm to track the Head and overlay an image over the Head. What I am doing is saving frames generated by camera and overlaying image over each frames. And time is not a constraint as I am not doing it Real-Time. My code…
Wazy
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HOG for "detecting object" opencv

I would like to know, if there is any code or any good documentation available for implementing HOG features? I tried to read the documentation here but it's quite difficult to understand and it needs SVM.. What I need is just to implement a HOG…
Mario
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convert OpenCV 2 vector to vector

The OpenCV 2 contour finder returns a vector, but sometimes you want to use these with a function that requires a vector. What is the fastest, most elegant way to convert? Here are some ideas. A very general conversion function for…
Kyle McDonald
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