ROS和opencv的使用关系
01基本工作原理
a. 为了便于ros与opencv联合使用,通过CvBridge库(ROS的一个库),提供ros与opencv间的接口;
b. CvBridge可以在cv_bridge包,在vision_opencv stack找到;
c. 各自图像格式及相互间的转换关系(ROS-sensor_msgs / Image传递图像格式/OpenCV cv :: Mat格式)
02代码实现示例
这是一个侦听ROS图像消息主题的节点,将图像转换为cv :: Mat,在其上绘制一个圆圈并使用OpenCV显示图像。然后通过ROS重新发布图像。
a. 在package.xml和CMakeLists.xml中(或使用catkin_create_pkg时),添加以下依赖项:
sensor_msgs
cv_bridge
roscpp
std_msgs
image_transport
b. 在/ src文件夹中创建image_converter.cpp文件并添加以下内容:
#include <ros/ros.h>
#include <image_transport/image_transport.h>//使用image_transport在ROS中发布和订阅图像,并允许您订阅压缩图像流。
#include <cv_bridge/cv_bridge.h>
#include <sensor_msgs/image_encodings.h>
#include <opencv2/imgproc/imgproc.hpp>
#include <opencv2/highgui/highgui.hpp>
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;
}