# OpenCV-Install-tutorial

**Repository Path**: mhguo/open-cv-install-tutorial

## Basic Information

- **Project Name**: OpenCV-Install-tutorial
- **Description**: How to install opencv4 in Ubuntu20.04
- **Primary Language**: Unknown
- **License**: Not specified
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2021-05-17
- **Last Updated**: 2023-03-25

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

# Tutorial: How to install OpenCV-4.7.0 in Ubuntu22.0

- date: 2021-5-17
- update: 2023-3-25
- by: mhguo
- environment: 
  - OpenCV-4.7.0, 
  - Ubuntu 22.04.2 LTS on VMware 17 Pro
- reference: [How to install OpoenCV 4 on Ubuntu](https://www.pyimagesearch.com/2018/08/15/how-to-install-opencv-4-on-ubuntu/)

---

## Step0: Change sources and update

## Step1: Install OpenCV4 dependencies on Ubuntu

```bash
# update system
sudo apt-get update
sudo apt-get upgrade

# install developer tools:
sudo apt-get install build-essential cmake unzip pkg-config

# install a handful of image and vide I/O libraries.
sudo apt-get install libjpeg-dev libpng-dev libtiff-dev
sudo apt-get install libavcodec-dev libavformat-dev libswscale-dev libv4l-dev
sudo apt-get install install libxvidcore-dev libx264-dev

# install GTK for our GUI backed:
sudo apt-get install libgtk-3-dev

# install two packages which contain mathematical optimizations for OpenCV:
sudo apt-get install libatlas-base-dev gfortran

# install Python3 development headers:
sudo apt-get install python3-dev
```

## Step2: Download, Unzip, MV OpenCV files.

- copy zip files to ~.

```bash
cd ~
#wget -O opencv.zip https://github.com/opencv/opencv/archive/4.7.0.zip
#wget -O opencv_contrib.zip https://github.com/opencv/opencv_contrib/archive/4.7.0.zip
unzip opencv.zip
unzip opencv_contrib.zip
# Rename
mv opencv-4.7.0 opencv
mv opencv_contrib-4.7.0 opencv_contrib
```

> `opencv.zip` and `opencv_contrib.zip` has already been downloaded in this repository.

## Step3: Configure python3 virtual environment

- copy `get-pip.py` to ~.

```bash
cd ~
#wget https://bootstrap.pypa.io/get-pip.py
sudo python3 get-pip.py
sudo pip install virtualenv virtualenvwrapper
sudo rm -rf ~/get-pip.py ~/.cache/pip
```

Using `nano` to open  `~/.bashrc` file:

```bash
sudo nano ~/.bashrc
```

Add 3 lines below to the end of `~/.bashrc` file.

```bash
export WORKON_HOME=$HOME/.virtualenvs
export VIRTUALENVWRAPPER_PYTHON=/usr/bin/python3
source /usr/local/bin/virtualenvwrapper.sh
```

Update source file like this: 

````bash
source ~/.bashrc
````

Create virtual environment (py3cv4) using below cmd:

```bash
mkvirtualenv py3cv4 -p python3
```

When virtual environment is created, using `workon` to active such env:

```bash
workon py3cv4
```

Install numpy

```bash
pip install numpy
```

## Step4: Compile  OpenCV and link it to Virtual Python

- cmake and make OpenCV4 **(Warning: running in virtual environment `py3cv4` )**

  ```bash
  cd ~/opencv
  mkdir build
  cd build
  
  cmake -D CMAKE_BUILD_TYPE=RELEASE \
        -D CMAKE_INSTALL_PREFIX=/usr/local \
        -D INSTALL_PYTHON_EXAMPLES=ON \
        -D INSTALL_C_EXAMPLES=OFF \
        -D OPENCV_ENABLE_NONFREE=ON \ #using nonfree modules
        -D OPENCV_EXTRA_MODULES_PATH=~/opencv_contrib/modules \
        -D PYTHON_EXECUTABLE=~/.virtualenvs/py3cv4/bin/python \ # Warning: vir name must be the same
        -D BUILD_EXAMPLES=ON ..
  
  make -j4 #according to the number of CPU
  sudo make install
  sudo ldconfig
  ```

- NOTE: check results of `cmake`

- **Important**: link OpenCV4 to virtual environment

  - Step1: Check `cv2.so`:

    ```bash
    ls /usr/local/lib/python3.8/site-packages/cv2/python-3.8/
    ```

    it will return: `cv2.cpython-38-x86_64-linux-gnu.so`

  - Step2: Rename to simple `cv2.so`:

    ```bash
    cd /usr/local/lib/python3.8/site-packages/cv2/python-3.8/
    sudo mv cv2.cpython-38-x86_64-linux-gnu.so cv2.so
    ```

  - Step3: Make link

    ```bash
    cd ~/.virtualenvs/py3cv4/lib/python3.8/site-packages
    ln -s /usr/local/lib/python3.8/site-packages/cv2/python-3.8/cv2.so cv2.so
    ```

---



# OpenCV Test:

- check the version of OpenCV in python terminal:

  ```bash
  workon py3cv4
  python
  import cv2
  print(cv2.__version__)
  ```

  

- In folder `OpenCV_Basic_Demos`, a demo `.py` file is created for the following tests:

  - test1: read and show a jpg picture.
  - test2: read and show a mp4 video.
  - test3: read and show a live camera.

- If the camera is connected but not work, check if USB 3.0 is used.