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opencv入门教程

article 2024/9/22 10:04:16

文章目录

- opencv简介
- - opencv使用
  - - CMakeLists.txt文件说明:
  - 实例
  - - 图形图像的处理
    - 视频处理
    - 视频监控
- 图像与图形
- 图形绘制
- 人脸识别与标记
- 文本识别（车牌）

opencv简介

opencv是一个开源的计算机视觉库，可以用于图形图像和视频处理
安装：

直接安装

apt install libopencv-dev

自己编译

本体源码：
https://github.com/opencv/opencv/releases/tag/4.2.0
扩展库源码：
https://github.com/opencv/opencv_contrib/releases

opencv使用

使用OpenCV进行开发

搭建环境
工具链
C程序的编译过程 – 自动编译管理工具make – 通过Makefile文件来指定自动编译的过程和步骤 – cmake – 通过CMakeLists.txt文件来输出/生产Makefile文件

CMakeLists.txt文件说明:

# cmake needs this line
cmake_minimum_required(VERSION 3.1)

# 定义工程的名字
project(Project_OpenCV_0628)

# 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}")

# 定义使用什么源文件生成指定得输出文件
add_executable(opencv_test video_capture_test.cpp)

# 指定生成输出文件使用得库
target_link_libraries(opencv_test PRIVATE ${OpenCV_LIBS})

实例

图形图像的处理

使用OpenCV库实现图形图像的处理

在工作目录下，新建一个项目的目录
china@ubuntu:~$ mkdir Project_OpenCV_0530
在项目目录中新建两个文件: test.cpp, CMakeLists.txt
china@ubuntu:~$ cd Project_OpenCV_0530/
china@ubuntu:~/Project_OpenCV_0530$ touch test.cpp
china@ubuntu:~/Project_OpenCV_0530$ touch CMakeLists.txt
在项目目录下新建一个目录: build
china@ubuntu:~/Project_OpenCV_0530$ mkdir build
china@ubuntu:~/Project_OpenCV_0530$ ls
build CMakeLists.txt test.cpp
编写CMakeLists.txt文件

# cmake needs this line
cmake_minimum_required(VERSION 3.1)

# 定义工程的名字
project(Project_OpenCV_0530)

# 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}")

# 定义使用什么源文件生成指定得输出文件
add_executable(opencv_test test.cpp)

# 指定生成输出文件使用得库
target_link_libraries(opencv_test PRIVATE ${OpenCV_LIBS})

编写cpp文件
先拷贝一个图片文件放到Linux工作目录: bbb.jpg
编写C++源文件:

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

using namespace std;
using namespace cv;  //OpenCV的命名空间

int main(int argc, char *argv[])
{
	Mat img = imread("/home/china/bbb.jpg");
	imshow("OpenCV显示图片", img);

	waitKey(0);

	return 0;
}

编译
先进入到build目录，执行cmake，生产Makefile文件

cd build/
cmake ..
ls
CMakeCache.txt  CMakeFiles  cmake_install.cmake  Makefile

编译

make
Scanning dependencies of target opencv_test
[ 50%] Building CXX object CMakeFiles/opencv_test.dir/test.cpp.o
[100%] Linking CXX executable opencv_test
[100%] Built target opencv_test

运行
./opencv_test

视频处理

在Project_OpenCV_0530目录下新建一个C++源文件

video_test.cpp
china@ubuntu:~/Project_OpenCV_0530/build$ cd ..
china@ubuntu:~/Project_OpenCV_0530$ touch video_test.cpp

编写C++源文件

#include <iostream>
#include <opencv2/opencv.hpp>
#include <opencv2/highgui.hpp>
#include <opencv2/imgproc.hpp>
#include <opencv2/videoio.hpp>

using namespace std;
using namespace cv;

int main(int argc, char *argv[])
{
	VideoCapture video;

	video.open("/home/china/test.avi");
	if(!video.isOpened())
	{
		return -1;
	}

	while(true)
	{
		Mat img;
		video >> img;
		if(!img.empty())
		{
			imshow("视频显示", img);
		}
		if(waitKey(30) > 0)
		{
			break;
		}
	}

	return 0;
}

修改CMakeLists.txt文件

# 定义使用什么源文件生成指定得输出文件
add_executable(opencv_test video_test.cpp)

编译

china@ubuntu:~/Project_OpenCV_0530$ cd build
china@ubuntu:~/Project_OpenCV_0530/build$ cmake ..
-- OpenCV library status:
--     config: /usr/local/lib/cmake/opencv4
--     version: 4.5.1
--     libraries: 
-- Configuring done
-- Generating done
-- Build files have been written to: /home/china/Project_OpenCV_0530/build
china@ubuntu:~/Project_OpenCV_0530/build$ make
Scanning dependencies of target opencv_test
[ 50%] Building CXX object CMakeFiles/opencv_test.dir/video_test.cpp.o
[100%] Linking CXX executable opencv_test
[100%] Built target opencv_test

执行
china@ubuntu:~/Project_OpenCV_0530/build$ ./opencv_test

视频监控

#include <iostream>
#include <opencv2/opencv.hpp>
#include <opencv2/highgui.hpp>
#include <opencv2/imgproc.hpp>
#include <opencv2/videoio.hpp>

using namespace std;
using namespace cv;

int main(int argc, char *argv[])
{
	VideoCapture video(0);
	if(!video.isOpened())
	{
		return -1;
	}

	Mat img;
	while(true)
	{
		video >> img;
		imshow("视频监控", img);
		
		if(waitKey(30) >= 0)
		{
			break;
		}
	}

	waitKey(0);

	return 0;
}