00037-Using OpenCV with gcc and CMake-ubuntu

前言

OpenCV 的官网地址为：https://opencv.org/ 。

OpenCV Tutorials 的地址为：https://docs.opencv.org/4.x/d9/df8/tutorial_root.html 。

原教程链接: https://docs.opencv.org/4.x/db/df5/tutorial_linux_gcc_cmake.html .

操作系统：Ubuntu 20.04.5 LTS

参考文档

Using OpenCV with gcc and CMake

安装 `OpenCV`

操作系统:

$ hostnamectl
   Static hostname: lyfubuntu
         Icon name: computer-desktop
           Chassis: desktop
        Machine ID: 5035e8d52f2e4471805511e24788918c
           Boot ID: b20ae92003504b5d9bdee983093f9ea6
  Operating System: Ubuntu 20.04.5 LTS
            Kernel: Linux 5.15.0-53-generic
      Architecture: x86-64

安装 OpenCV:

1	$ sudo apt install libopencv-dev

g++, cmake 和 make:

$ g++ --version
g++ (Ubuntu 9.4.0-1ubuntu1~20.04.1) 9.4.0
Copyright (C) 2019 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ cmake --version
cmake version 3.16.3

CMake suite maintained and supported by Kitware (kitware.com/cmake).
$ make --version
GNU Make 4.2.1
为 x86_64-pc-linux-gnu 编译
Copyright (C) 1988-2016 Free Software Foundation, Inc.
许可证：GPLv3+：GNU 通用公共许可证第 3 版或更新版本<http://gnu.org/licenses/gpl.html>。
本软件是自由软件：您可以自由修改和重新发布它。
在法律允许的范围内没有其他保证。

使用 OpenCV 创建程序

创建一个名为 DisplayImage.cpp 的文件, 如下所示.

#include <stdio.h>
#include <opencv2/opencv.hpp>
using namespace cv;
int main(int argc, char** argv )
{
    if ( argc != 2 )
    {
        printf("usage: DisplayImage.out <Image_Path>\n");
        return -1;
    }
    Mat image;
    image = imread( argv[1], 1 );
    if ( !image.data )
    {
        printf("No image data \n");
        return -1;
    }
    namedWindow("Display Image", WINDOW_AUTOSIZE );
    imshow("Display Image", image);
    waitKey(0);
    return 0;
}

创建一个 CMake 文件

创建一个名为 CMakeLists.txt 的文件, 如下所示.

cmake_minimum_required(VERSION 2.8)
project( DisplayImage )
find_package( OpenCV REQUIRED )
include_directories( ${OpenCV_INCLUDE_DIRS} )
add_executable( DisplayImage DisplayImage.cpp )
target_link_libraries( DisplayImage ${OpenCV_LIBS} )

添加图片

在文件 DisplayImage.cpp 所在目录添加一个名为 susu.jpg 的图片.

生成可执行文件并运行

$ ls
CMakeLists.txt  DisplayImage.cpp  susu.jpg
$ mkdir build
$ cd build/
$ cmake ..
-- The C compiler identification is GNU 9.4.0
-- The CXX compiler identification is GNU 9.4.0
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Found OpenCV: /usr (found version "4.2.0") 
-- Configuring done
-- Generating done
-- Build files have been written to: /home/lyfubuntu/my_computer_language/temp/temp/build
$ make
Scanning dependencies of target DisplayImage
[ 50%] Building CXX object CMakeFiles/DisplayImage.dir/DisplayImage.cpp.o
[100%] Linking CXX executable DisplayImage
[100%] Built target DisplayImage
$ ls
CMakeCache.txt  CMakeFiles  cmake_install.cmake  DisplayImage  Makefile
$ ./DisplayImage ../susu.jpg 
$