【笔记】Compile and install OpenCV on Linux

OpenCV Build

This article is used to practice English and record the process of operation

1. Clone the OpenCV repository from Github

# Clone the original repository
git clone https://github.com/opencv/opencv.git
# Create a copy for version 3.2.0
cp -r opencv opencv-3.2
# Switch to version 3.2.0
cd opencv-3.2 && git checkout 3.2.0

# Return to the root directory
cd ..
# Create a copy for version 4.11.0
cp -r opencv opencv-4.11
# Switch to version 4.11.0
cd opencv-4.11 && git checkout 4.11.0

2. Clone the opencv_contrib repository from Github

# Clone the original repository
git clone https://github.com/opencv/opencv_contrib.git
# Create a copy for version 3.2.0
cp -r opencv_contrib opencv_contrib-3.2
# Switch to version 3.2.0
cd opencv_contrib-3.2 && git checkout 3.2.0

# Return to the root directory
cd ..
# Create a copy for version 4.11.0
cp -r opencv_contrib opencv_contrib-4.11
# Switch to version 4.11.0
cd opencv_contrib-4.11 && git checkout 4.11.0

3. Build & Install

This section demonstrates how to build and install OpenCV version 4.11.0.

3.1 Create a build directory

cd ~/opencv-build/opencv
mkdir build && cd build

3.2 Build with CMake

cmake -D CMAKE_BUILD_TYPE=Release \
      -D CMAKE_INSTALL_PREFIX=/usr/local/opencv-4.11 \
      -D OPENCV_EXTRA_MODULES_PATH=~/opencv-build/opencv_contrib-4.11/modules \
      -D BUILD_opencv_gapi=ON \
      -D OPENCV_GENERATE_PKGCONFIG=ON \
      -D BUILD_EXAMPLES=ON \
      -D ENABLE_PRECOMPILED_HEADERS=OFF ..

Parameters Description：

• CMAKE_BUILD_TYPE=Release：Compile to an optimized release version.
• CMAKE_INSTALL_PREFIX=/usr/local/opencv-4.11：Specify the installation path so that it is isolated from other version.
• BUILD_opencv_gapi：Compile the OpenCV Graph API.
• OPENCV_GENERATE_PKGCONFIG：Generate a .pc file for pkgconfig.
• OPENCV_EXTRA_MODULES_PATH：Specify the opencv_contrib module path.
• BUILD_EXAMPLES=ON：Compile the example code (Optional).

3.3 Compile & Install on Linux

# Compile using all avaliable core
make -j$(nproc)
# Install（requires sudo privileges）
sudo make install

4. Configuration the pkg-config

4.1 Edit the Configuration File

Use Vim to open your ~/.bashrc file , and append the path to the opencv4.pc to the PKG_CONFIG_PATH envronment variable：

# At the end of ~/.bashrc 
export PKG_CONFIG_PATH=$PKG_CONFIG_PATH:/usr/local/opencv-4.11/lib/pkgconfig/

4.2 Enable the ~/.bashrc Configuration

To apply the changes, reload your ~/.bashrc file with the following command：

source ~/.bashrc

4.3 Add OpenCV to Dynamic Linker

Create an opencv4.conf file in the /etc/ld.so.conf.d/ directory that contains the path to OpenCV`s lib directory.

# /etc/ld.so.conf.d/opencv4.conf
/usr/local/opencv-4.11/lib

4.4 Refresh the Dynamic Linker Cache on Linux

To Update the dynamic linker cache, run:

sudo ldconfig

4.5 Verify pkg-config command output

Verify that pkg-config can correctly locate OpenCV by running：

pkg-config --modversion opencv4

At this point, the output should be：

4.11.0

5 Reference

• 详尽指南：在 Ubuntu 20.04 中源码编译安装 OpenCV 并进行全面配置，包括多版本共存与切换