In this post I will guide you guys, how can you port nodes to nodelets in ROS.
The nodelet package is designed to provide a way to run multiple algorithms in the same process with zero copy transport between algorithms nodelet_from_ros_wiki.
Let's take an very simple example of subscribing to color image from kinect and publishing it un-modified.
// The following snippets are written using C++
//Entrypoint in main.cpp
int main (int argc, char** argv)
{
ros::init(argc, argv,"node_name");
ros::NodeHandle node;
ros::NodeHandle priv_nh("~");
package_name::node_class class_object(node,priv_nh);
ros::spin();
return 0;
}
//node_class.h
// include all the header files here
namespace package_name
{
class node_class
{
public:
node_class(ros::NodeHandle node,ros::NodeHandle private_nh);
~node_class(){};
void image_callback(const sensor_msgs::ImageConstPtr& msg);
private:
image_transport::Subscriber image_sub_;
image_transport::Publisher image_pub_;
}
}
//Define the node class
// node_class.cpp
namespace package_name
{
node_class::node_class (ros::NodeHandle ndoe, ros::NodeHandle private_nh)
{
image_transport::ImageTransport it_(node);
image_sub_ = it_.subscribe("/camera/rgb/image_rect_color",1,&node_class::image_callback,this) ;
} //constructor
// define the image_callback, for now I just display the input image as it is, you can do all the modifications to the input image here and then publish it.
void node_class::image_callback(const sensor_msgs::ImageConstPtr& msg)
{
cv_bridge::CvImagePtr cv_ptr;
try
{
cv_ptr = cv_bridge::toCvCopy(msg, enc::BGR8);
}
catch (cv_bridge::Exception& e)
{
ROS_ERROR("cv_bridge exception: %s", e.what());
return;
}
cv::imshow("in image", cv_ptr->image);
cv::waitKey(3);
image_pub_.publish(cv_ptr->toImageMsg());
} // image_callback
} // namespace
//nodelet_class.h
#include <nodelet/nodelet.h>
#include "node_class.h"
namespace package_name{
class nodelet_class: public nodelet::Nodelet
{
public:
nodelet_class(){}
~nodelet_class(){}
virtual void onInit();
boost::shared_ptr<node_class> inst_;
};
}
//Define the nodelet class
//nodelet_class.cpp
#include <nodelet/nodelet.h>
#include <pluginlib/class_list_macros.h>
#include "nodelet_class.h"
namespace package_name
{
void nodelet_class::onInit()
{
NODELET_DEBUG("Initializing nodelet");
inst_.reset(new node_class(getNodeHandle(), getPrivateNodeHandle()));
}
}
PLUGINLIB_DECLARE_CLASS(package_name,nodelet_class, package_name :nodelet_class, nodelet::Nodelet)
// now we have to export/add our nodelet in manifest.xml
<export>
<nodelet plugin="${prefix}/nodelet_plugins.xml" />
</export>
// Define nodelet as plugin in nodelet_plugins.xml
<library path="lib/libnodelet_class">
<class name="package_name/nodelet_class" type="package_name::nodelet_class" base_class_type="nodelet::Nodelet">
<description>
This is my nodelet.
</description>
</class>
</library>
//Finally we have to write a launch file for our nodelet in launch_nodelet.launch
<launch>
<node pkg="nodelet" type="nodelet" name="standalone_nodelet" args="manager" output="screen"/>
<node pkg="nodelet" type="nodelet" name="nodelet_class" args="load package_name/ nodelet_class standalone_nodelet" output="screen">
</node>
</launch>
##Note: Make sure you add a library for the nodelet_class which will be loaded while launching the nodelet in CMakeLists.txt
rosbuild_add_library(nodelet_class #add here the paths to all your source files)
Now launch the nodelet and enjoy faster image handling in ROS !!
The nodelet package is designed to provide a way to run multiple algorithms in the same process with zero copy transport between algorithms nodelet_from_ros_wiki.
Let's take an very simple example of subscribing to color image from kinect and publishing it un-modified.
// The following snippets are written using C++
//Entrypoint in main.cpp
int main (int argc, char** argv)
{
ros::init(argc, argv,"node_name");
ros::NodeHandle node;
ros::NodeHandle priv_nh("~");
package_name::node_class class_object(node,priv_nh);
ros::spin();
return 0;
}
//node_class.h
// include all the header files here
namespace package_name
{
class node_class
{
public:
node_class(ros::NodeHandle node,ros::NodeHandle private_nh);
~node_class(){};
void image_callback(const sensor_msgs::ImageConstPtr& msg);
private:
image_transport::Subscriber image_sub_;
image_transport::Publisher image_pub_;
}
}
//Define the node class
// node_class.cpp
namespace package_name
{
node_class::node_class (ros::NodeHandle ndoe, ros::NodeHandle private_nh)
{
image_transport::ImageTransport it_(node);
image_sub_ = it_.subscribe("/camera/rgb/image_rect_color",1,&node_class::image_callback,this) ;
} //constructor
// define the image_callback, for now I just display the input image as it is, you can do all the modifications to the input image here and then publish it.
void node_class::image_callback(const sensor_msgs::ImageConstPtr& msg)
{
cv_bridge::CvImagePtr cv_ptr;
try
{
cv_ptr = cv_bridge::toCvCopy(msg, enc::BGR8);
}
catch (cv_bridge::Exception& e)
{
ROS_ERROR("cv_bridge exception: %s", e.what());
return;
}
cv::imshow("in image", cv_ptr->image);
cv::waitKey(3);
image_pub_.publish(cv_ptr->toImageMsg());
} // image_callback
} // namespace
//nodelet_class.h
#include <nodelet/nodelet.h>
#include "node_class.h"
namespace package_name{
class nodelet_class: public nodelet::Nodelet
{
public:
nodelet_class(){}
~nodelet_class(){}
virtual void onInit();
boost::shared_ptr<node_class> inst_;
};
}
//Define the nodelet class
//nodelet_class.cpp
#include <nodelet/nodelet.h>
#include <pluginlib/class_list_macros.h>
#include "nodelet_class.h"
namespace package_name
{
void nodelet_class::onInit()
{
NODELET_DEBUG("Initializing nodelet");
inst_.reset(new node_class(getNodeHandle(), getPrivateNodeHandle()));
}
}
PLUGINLIB_DECLARE_CLASS(package_name,nodelet_class, package_name :nodelet_class, nodelet::Nodelet)
// now we have to export/add our nodelet in manifest.xml
<export>
<nodelet plugin="${prefix}/nodelet_plugins.xml" />
</export>
// Define nodelet as plugin in nodelet_plugins.xml
<library path="lib/libnodelet_class">
<class name="package_name/nodelet_class" type="package_name::nodelet_class" base_class_type="nodelet::Nodelet">
<description>
This is my nodelet.
</description>
</class>
</library>
//Finally we have to write a launch file for our nodelet in launch_nodelet.launch
<launch>
<node pkg="nodelet" type="nodelet" name="standalone_nodelet" args="manager" output="screen"/>
<node pkg="nodelet" type="nodelet" name="nodelet_class" args="load package_name/ nodelet_class standalone_nodelet" output="screen">
</node>
</launch>
##Note: Make sure you add a library for the nodelet_class which will be loaded while launching the nodelet in CMakeLists.txt
rosbuild_add_library(nodelet_class #add here the paths to all your source files)
Now launch the nodelet and enjoy faster image handling in ROS !!
