ROS Sensor_msgs/Image与OpenCV Mat互转

一、摘要

ROS 以自己的 sensor_msgs/Image 消息格式传递图像，但许多用户希望将图像与 OpenCV 结合使用。 CvBridge 是一个 ROS 库，提供 ROS 和 OpenCV 之间的接口。 CvBridge 可以在 vision_opencv 堆栈中的 cv_bridge 包中找到。

 二、干货

需要的头文件

#include "ros/ros.h"
#include 
#include 
#include "opencv2/opencv.hpp"

A）cv::Mat 转 sensor_msgs::Image

cv::Mat image;
sensor_msgs::ImagePtr msg = cv_bridge::CvImage(std_msgs::Header(), "bgr8", image).toImageMsg();

B）sensor_msgs::Image 转 cv::Mat

cv_bridge::CvImagePtr cv_ptr = cv_bridge::toCvCopy(msg, sensor_msgs::image_encodings::TYPE_8UC3);
cv::Mat img = cv_ptr->image;

三、一个小Demo

#include 
#include 
#include 
#include 
#include 
#include 

static const std::string OPENCV_WINDOW = "Image window";

class ImageConverter
{
  ros::NodeHandle nh_;
  image_transport::ImageTransport it_;
  image_transport::Subscriber image_sub_;
  image_transport::Publisher image_pub_;

public:
  ImageConverter()
    : it_(nh_)
  {
    // Subscrive to input video feed and publish output video feed
    image_sub_ = it_.subscribe("/camera/image_raw", 1,
      &ImageConverter::imageCb, this);
    image_pub_ = it_.advertise("/image_converter/output_video", 1);

    cv::namedWindow(OPENCV_WINDOW);
  }

  ~ImageConverter()
  {
    cv::destroyWindow(OPENCV_WINDOW);
  }

  void imageCb(const sensor_msgs::ImageConstPtr& msg)
  {
    cv_bridge::CvImagePtr cv_ptr;
    try
    {
      cv_ptr = cv_bridge::toCvCopy(msg, sensor_msgs::image_encodings::BGR8);
    }
    catch (cv_bridge::Exception& e)
    {
      ROS_ERROR("cv_bridge exception: %s", e.what());
      return;
    }

    // Draw an example circle on the video stream
    if (cv_ptr->image.rows > 60 && cv_ptr->image.cols > 60)
      cv::circle(cv_ptr->image, cv::Point(50, 50), 10, CV_RGB(255,0,0));

    // Update GUI Window
    cv::imshow(OPENCV_WINDOW, cv_ptr->image);
    cv::waitKey(3);

    // Output modified video stream
    image_pub_.publish(cv_ptr->toImageMsg());
  }
};

int main(int argc, char** argv)
{
  ros::init(argc, argv, "image_converter");
  ImageConverter ic;
  ros::spin();
  return 0;
}

四、参考

cv_bridge/Tutorials/UsingCvBridgeToConvertBetweenROSImagesAndOpenCVImages - ROS Wiki