Installation and use of OpenCV3.4.11 under Ubuntu 18.04

catalogue

(1) Installation package

1. Download OpenCV 3.4.11 data package. Domestic fast download address: OpenCV/opencv_contrib domestic fast download | cloud technology blog

2. Decompression

Before decompressing the package, copy opencv-3.4.11.zip to the home directory folder, and then decompress it.

3. Install opencv

Enter the command to enter the extracted folder

cd opencv-3.4.11

Enter command: sudo su Then execute the installation command

sudo apt-get install cmake

Then install the dependent libraries:

sudo apt-get install build-essential libgtk2.0-dev libavcodec-dev libavformat-dev libjpeg.dev libtiff5.dev libswscale-dev

Create the build folder, and then enter the created folder

mkdir build cd build

Compile the parameter using cmake, or use the second default parameter

cmake -D CMAKE_BUILD_TYPE=Release -D CMAKE_INSTALL_PREFIX=/usr/local .. cmake ..

4. Use make to create a compiler

sudo make

5. Installation

After compiling, enter the command:

sudo make install

Wait for the installation to complete.

(2) Configuration environment

Enter command:

sudo gedit /etc/ld.so.conf.d/opencv.conf

After that, you can modify the opencv.conf file. You can find that the file is empty. Add the installation path of OpenCV Library: / usr/local/lib

Click save, and then return to the terminal. You can find that there is a warning message, there is no impact, or the command is input normally.

Input:

sudo ldconfig

Update the system shared link library and enter:

sudo gedit /etc/bash.bashrc

Configure Bash and modify the bash.bashrc file.

The text editor opens

Add at the end of the document

PKG_CONFIG_PATH=$PKG_CONFIG_PATH:/usr/local/lib/pkgconfig export PKG_CONFIG_PATH

Click save, then exit... And enter the command to make the configuration effective.

source /etc/bash.bashrc

Input instruction: sudo updatedb To update

Input command:

pkg-config --modversion opencv

Check the version of opencv we installed and find that it is 3.4.11. The installation is over.

2, Pictures of OpenCv usage examples

First, create a folder for storing code. Here I name it code1. Enter the following command to create and enter the folder

mkdir code1 cd code1

Create a test1.cpp file

vim test1.cpp

Then enter the following code:

#include <opencv2/highgui.hpp> #include <opencv2/opencv.hpp> using namespace cv; using namespace std; int main(int argc, char** argv) { CvPoint center; double scale = -3; IplImage* image = cvLoadImage("lena.jpg"); argc == 2? cvLoadImage(argv[1]) : 0; cvShowImage("Image", image); if (!image) return -1; center = cvPoint(image->width / 2, image->height / 2); for (int i = 0;i<image->height;i++) for (int j = 0;j<image->width;j++) { double dx = (double)(j - center.x) / center.x; double dy = (double)(i - center.y) / center.y; double weight = exp((dx*dx + dy*dy)*scale); uchar* ptr = &CV_IMAGE_ELEM(image, uchar, i, j * 3); ptr[0] = cvRound(ptr[0] * weight); ptr[1] = cvRound(ptr[1] * weight); ptr[2] = cvRound(ptr[2] * weight); } Mat src;Mat dst; src = cvarrToMat(image); cv::imwrite("test.png", src); cvNamedWindow("test",1); imshow("test", src); cvWaitKey(); return 0; }

Execute the following command to compile the file

g++ test1.cpp -o test1 `pkg-config --cflags --libs opencv`

Prepare a picture in the same folder with the file name lena.jpg

Input instruction:. / test

You can see that lena.jpg generates a test.png, and the picture is different

3, Video of an example of OpenCv

(1) Get camera permissions for virtual machine

Under windows, use the shortcut key Win + R, enter services.msc, and press enter.

Locate the VMware USB Arbitration S... Service and make sure it starts.

Click virtual machine, and then click Settings.

Select "USB controller", set "USB compatibility" to "USB 3.0", and click OK.

Select "virtual machine", then select "removable device", and then select the camera name of your device, such as Quanta USB2.0 VGA UVC WebCam ， Finally, click "connect", and then click "OK" in the pop-up window.

After the connection is successful, you can see the green dot in the lower right corner of the virtual machine.

(2) Video playback

Create a test2.cpp file

Enter the following code:

#include <opencv2/opencv.hpp> using namespace cv; int main() { //Read video from camera VideoCapture capture("man.mp4"); //Cycle through each frame while(1){ Mat frame;//Define a Mat variable to store the image of each frame capture >> frame;//Read current frame if(frame.empty())//Play finished, exit break; imshow("Read video frame",frame);//Displays the current frame waitKey(30);//Cover up 30ms } system("pause"); return 0; }

Download a video from the browser. Here is a man.mp4

Compile test2.cpp

g++ test2.cpp -o test2 `pkg-config --cflags --libs opencv`

Output results

./test2

You can find the video playing.

(3) Video recording

Create a test3.cpp file

Enter the following code:

/********************************************************************* Turn on the computer camera, control the video recording with a blank space, and ESC exits and saves the video RecordVideo.avi *********************************************************************/ #include<iostream> #include <opencv2/opencv.hpp> #include<opencv2/core/core.hpp> #include<opencv2/highgui/highgui.hpp> using namespace cv; using namespace std; int main() { //Turn on the computer camera VideoCapture cap(0); if (!cap.isOpened()) { cout << "error" << endl; waitKey(0); return 0; } //Get the resolution of cap int w = static_cast<int>(cap.get(CV_CAP_PROP_FRAME_WIDTH)); int h = static_cast<int>(cap.get(CV_CAP_PROP_FRAME_HEIGHT)); Size videoSize(w, h); VideoWriter writer("RecordVideo.avi", CV_FOURCC('M', 'J', 'P', 'G'), 25, videoSize); Mat frame; int key;//Record keyboard keys char startOrStop = 1;//0 starts recording video; 1 end recording video char flag = 0;//Recording flag 0 - not recording; 1 - recording while (1) { cap >> frame; key = waitKey(100); if (key == 32)//Press the space to start recording and pause recording to switch back and forth { startOrStop = 1 - startOrStop; if (startOrStop == 0) { flag = 1; } } if (key == 27)//Press ESC to exit the whole program and save the video file to disk { break; } if (startOrStop == 0 && flag==1) { writer << frame; cout << "recording" << endl; } else if (startOrStop == 1) { flag = 0; cout << "end recording" << endl; } imshow("picture", frame); } cap.release(); writer.release(); destroyAllWindows(); return 0; }

Compile test3.cpp with the input code