【opencv】ubuntu安装opencv4.2.0（支持cuda加速）

转载自:https://blog.youkuaiyun.com/dulingwen/article/details/90607767

一、下载opencv

网址：https://github.com/opencv

可以进入github下载，也可使用如下命令下载：

git clone https://github.com/Itseez/opencv.git
git clone https://github.com/Itseez/opencv_contrib.git      # gpu加速支持

下载后，将opencv_contrib文件夹移动到opencv中去。

二、安装opencv所需要的依赖库：

sudo apt-get install build-essential
sudo apt-get install cmake git libgtk2.0-dev pkg-config libavcodec-dev libavformat-dev libswscale-dev
sudo apt-get install python-dev python-numpy libtbb2 libtbb-dev libjpeg-dev libpng-dev libtiff-dev libjasper-dev libdc1394-22-dev

里面有些东西诸如cmake、git、python-dec、python-numpy一般早都安装好了，确定的话可以直接去掉。

三、编译opencv

1.opencv目录下，创建build文件夹
mkdir build

2.进入build目录，执行cmake命令：
参考第二篇文章不加opencv_contrib的编译

cmake -D CMAKE_INSTALL_PREFIX=/usr/local -D CMAKE_BUILD_TYPE=Release -D OPENCV_GENERATE_PKGCONFIG=ON -D ENABLE_CXX11=1 -D OPENCV_ENABLE_NONFREE=True ..

• 编译生成libopencv_world.so
  -D BUILD_opencv_world=ON

不要GPU加速支持

cmake -D CMAKE_INSTALL_PREFIX=/usr/local -D CMAKE_BUILD_TYPE=Release -D OPENCV_GENERATE_PKGCONFIG=ON -D ENABLE_CXX11=1 -D OPENCV_EXTRA_MODULES_PATH=../opencv_contrib/modules -D OPENCV_ENABLE_NONFREE=True ..

需要支持GPU加速：

cmake -D CMAKE_INSTALL_PREFIX=/usr/local -D CMAKE_BUILD_TYPE=Release -D OPENCV_GENERATE_PKGCONFIG=ON -D ENABLE_CXX11=1 -D OPENCV_EXTRA_MODULES_PATH=../opencv_contrib/modules -D OPENCV_ENABLE_NONFREE=True -D INSTALL_PYTHON_EXAMPLES=ON -D INSTALL_C_EXAMPLES=ON -D WITH_CUDA=ON -D WITH_TBB=ON -D ENABLE_FAST_MATH=1 -D WITH_OPENMP=ON -D WITH_CUFFT=ON -D WITH_CUBLAS=ON ..

注意：上面的cmake命令必须按照我的执行。

3.使用make开始编译
make -j8
-j8是同时使用8核CPU来执行编译过程，这样速度比较快，具体需要根据自己的电脑情况修改。

可能报错：
error：calling a constexpr host function(“abs”) from a device function(“abs”) is not allowed. The experimental flag ‘–expt-relaxed-constexpr’ can be used to allow this.

解决

这可能和显卡的型号有关，我是1070.

cmake时，添加编译选项-D CUDA_NVCC_FLAGS=–expt-relaxed-constexpr

4.编译install
sudo make install

然后在/usr/local/lib下可以看到编译的结果。

5.卸载opencv
sudo make uninstall

6.手动卸载opencv

sudo rm -r /usr/local/include/opencv4 
sudo rm -r /usr/local/include/opencv 
sudo rm -r /usr/include/opencv 
sudo rm -r /usr/include/opencv4 
sudo rm -r /usr/local/share/opencv 
sudo rm -r /usr/local/share/OpenCV 
sudo rm -r /usr/share/opencv 
sudo rm -r /usr/share/OpenCV 
sudo rm -r /usr/local/bin/opencv* 
sudo rm -r /usr/local/lib/libopencv*
sudo rm -r /usr/local/lib/pkgconfig/opencv4.pc
sudo rm -r /usr/local/lib/cmake/opencv4

四、配置环境

1.配置pkg-config路經

经过上面的步骤后，在/usr/local/lib/pkgconfig下生成了opencv4.pc文件，这个文件很重要，里面记录了OpenCV头文件、库文件的路經。需要进行如下配置：

#进入 bash.bashrc
sudo gedit /etc/bash.bashrc
 
#在文件最后添加如下内容
PKG_CONFIG_PATH=$PKG_CONFIG_PATH:/usr/local/lib/pkgconfig
export PKG_CONFIG_PATH
 
#更新
sudo updatedb

可参考:linux下编译安装opencv生成opencv.pc ，pkg-config的设置

2.配置库路經

#打开下列文件
sudo gedit /etc/ld.so.conf.d/opencv.conf 
 
# 添加lib路經
/usr/local/lib
 
# 更新
sudo ldconfig

NOTE：一切有关” cannot open shared object file: No such file or directory “的问题基本都可以通过上面的方式来解决（除非是操作系统里确实没有包含该共享库(lib*.so.*文件)或者共享库版本不对）

查看opencv版本号：

pkg-config --modversion opencv4

五、程序测试

1. 在一个文件夹下，编写一个main.cpp文件，内容如下：

#include <iostream>
#include <opencv2/opencv.hpp>

using namespace std;
using namespace cv;

int main() {
    Mat img = imread("/home/yangna/deepblue/32_face_detect/centerface/readme/test.png");
    imshow("mat", img);
    waitKey(5000);
    std::cout << "Hello, World!" << std::endl;
    return 0;
}

2. 编写CMakeLists.txt文件
这个步骤，最简单的方式是去opencv的文件夹里直接复制一份过来，位置：/opencv/samples/cpp/example_cmake下，在里面修改部分内容如下所示：

#cmake_minimum_required(VERSION 3.14)
#project(4_test_opencv)
#
#set(CMAKE_CXX_STANDARD 11)
#
#add_executable(4_test_opencv main.cpp)

# cmake needs this line
cmake_minimum_required(VERSION 3.1)

# Enable C++11
set(CMAKE_CXX_STANDARD 11)
set(CMAKE_CXX_STANDARD_REQUIRED TRUE)

# Define project name
project(4_test_opencv)

# Find OpenCV, you may need to set OpenCV_DIR variable
# to the absolute path to the directory containing OpenCVConfig.cmake file
# via the command line or GUI
find_package(OpenCV REQUIRED)

# If the package has been found, several variables will
# be set, you can find the full list with descriptions
# in the OpenCVConfig.cmake file.
# Print some message showing some of them
message(STATUS "OpenCV library status:")
message(STATUS "    config: ${OpenCV_DIR}")
message(STATUS "    version: ${OpenCV_VERSION}")
message(STATUS "    libraries: ${OpenCV_LIBS}")
message(STATUS "    include path: ${OpenCV_INCLUDE_DIRS}")

# Declare the executable target built from your sources
add_executable(4_test_opencv main.cpp)

# Link your application with OpenCV libraries
target_link_libraries(4_test_opencv LINK_PRIVATE ${OpenCV_LIBS})

3. 编译和运行
进入刚才的文件，执行以下命令

cmake .
make
./4_test_opencv

然后会显示一张图片5秒钟

reference

1. https://blog.youkuaiyun.com/dulingwen/article/details/90607767
2. https://blog.youkuaiyun.com/weixin_44003563/article/details/90404745