Open CV

Opencv (Open Source Computer Vision Library) is a library of programming functions mainly aimed at real-time computer version.

Get official release from SourceForge or get the latest sources from Github

Programming language

C++ interface. You can find API here.

Applications

All the links below need access to wikipedia, otherwise it is Unreachable.

• Facial recognition system
• Segmentation and recognition
• Object detection
• Motion tracking
• Gesture recognition
• others

OS support

• Windows, Linux, macOS etc.
• Android, iOS etc.

Installation in Linux

Environment: Fedora 35

# Install OpenCV from Fedora Linux Repository
sudo dnf install opencv opencv-contrib opencv-doc python3-opencv python3-matplotlib python3-numpy
# Test using Python
[limc@fedora Test]$ python
Python 3.10.1 (main, Jan 10 2022, 00:00:00) [GCC 11.2.1 20211203 (Red Hat 11.2.1-7)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import cv2 as cv
>>> print(cv.__version__)
4.5.3
>>> exit()

print(cv.__version__) tells the OpenCV version. That indicates that the OpenCV and Python OpenCV libraries have been successfully installed.

Test in cpp

First, we write a piece of code, which just read and show an GBR image.
Note, starry_night.jpg should be placed in the source code directory in this test.

#include <opencv2/core.hpp>
#include <opencv2/imgcodecs.hpp>
#include <opencv2/highgui.hpp>
#include <iostream>
using namespace cv;
int main()
{
    std::string image_path = samples::findFile("starry_night.jpg");
    Mat img = imread(image_path, IMREAD_COLOR);
    if(img.empty())
    {
        std::cout << "Could not read the image: " << image_path << std::endl;
        return 1;
    }
    imshow("Display window", img);
    int k = waitKey(0); // Wait for a keystroke in the window
    if(k == 's')
    {
        imwrite("starry_night.png", img);
    }
    return 0;
}

Then, we compile and run using commands below.

[limc@fedora Test]$ g++ display_image.cpp `pkg-config --cflags --libs opencv`
[limc@fedora Test]$ ./a.out

Result: