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目录

前言

一、创建包

二、创建节点

三、修改CMakeLists.txt及package.xml

四、编译运行

总结（最重要的）

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前言

ros教程：OpenCV调用usb摄像头

创建功能包教程在ROS教程（三）：创建程序包及节点（图文）已讲解，本文便不再细讲。

一、创建包

新建一个包名为 usb_cam，其中附加的依赖有std_msgs（消息传递），roscpp（c++），cv_bridge（ros和opencv图像转换），sensor_msgs（传感器消息），image_transport（图像编码传输）

cd catkin_ws/src

catkin_create_pkg usb_cam std_msgs roscpp cv_bridge sensor_msgs image_transport

二、创建节点

在usb_cam/src文件夹中添加两个cpp，一个发布图像消息img_publisher.cpp，一个接收并查看图像消息img_viewer.cpp

img_publisher.cpp

#include <ros/ros.h>
#include <image_transport/image_transport.h>
#include <opencv2/highgui.hpp>
#include <opencv2/calib3d.hpp>
#include <cv_bridge/cv_bridge.h>
#include <iostream>
 
int main(int argc, char** argv)
{
  ros::init(argc, argv, "img_publisher");
  ros::NodeHandle nh;
  image_transport::ImageTransport it(nh);
  image_transport::Publisher pub = it.advertise("camera/image", 1);
 
  cv::VideoCapture cap;
  cv::Mat frame;
  int deviceID=0;
  if(argc>1)
	deviceID=argv[1][0]-'0';
  int apiID=cv::CAP_ANY;
  cap.open(deviceID+apiID);
  if(!cap.isOpened()){
	std::cerr<<"ERROR! Unable to open camera"<<std::endl;
	return -1;
  }
 
  ros::Rate loop_rate(30);
  while (nh.ok()) {
	cap.read(frame);
	if(!frame.empty()){
		sensor_msgs::ImagePtr msg = cv_bridge::CvImage(std_msgs::Header(), "bgr8", frame).toImageMsg();
		pub.publish(msg);
	}
    	ros::spinOnce();
    	loop_rate.sleep();
  }
  return 0;
}

img_viewer.cpp

#include <ros/ros.h>
#include <image_transport/image_transport.h>
#include <opencv2/highgui/highgui.hpp>
#include <cv_bridge/cv_bridge.h>
 
void imageCallback(const sensor_msgs::ImageConstPtr& msg)
{
  try
  {
    cv::imshow("view", cv_bridge::toCvShare(msg, "bgr8")->image);
  }
  catch (cv_bridge::Exception& e)
  {
    ROS_ERROR("Could not convert from '%s' to 'bgr8'.", msg->encoding.c_str());
  }
}
 
int main(int argc, char **argv)
{
  ros::init(argc, argv, "img_viewer");
  ros::NodeHandle nh;
  cv::namedWindow("view");
  cv::startWindowThread();
  image_transport::ImageTransport it(nh);
  image_transport::Subscriber sub = it.subscribe("camera/image", 1, imageCallback);
  ros::spin();
  cv::destroyWindow("view");
  return 0;
}

三、修改CMakeLists.txt及package.xml

打开CMakeLists.txt可以看到ros的依赖库已经添加了，这里只需要再加上OpenCV的依赖并链接相应库就可以了。

find_package(catkin REQUIRED COMPONENTS
  cv_bridge
  image_transport
  roscpp
  sensor_msgs
  std_msgs
)
find_package(OpenCV REQUIRED)
 
include_directories(
  ${catkin_INCLUDE_DIRS}
  ${OpenCV_INCLUDE_DIRS}
)
 
add_executable(img_publisher src/img_publisher.cpp)
add_executable(img_viewer src/img_viewer.cpp)
 
target_link_libraries(img_publisher ${catkin_LIBRARIES} ${OpenCV_LIBS})
target_link_libraries(img_viewer ${catkin_LIBRARIES} ${OpenCV_LIBS})

接着修改package.xml文件，在里面添加

<build_depend>opencv2</build_depend>
<build_export_depend>opencv2</build_export_depend>
<exec_depend>opencv2</exec_depend>

四、编译运行

cd ~/catkin_ws
catkin_make

先启动ros

roscore

开两个终端分别启动节点

source ~/catkin_ws/devel/setup.bash
rosrun usb_cam img_publisher

source ~/catkin_ws/devel/setup.bash
rosrun usb_cam img_viewer

完成！

总结（最重要的）