Conversions

Converting data across libraries.

The data source/sink is:

Eigen

To go to/from messages, use eigen_conversions (or minkindr_conversions below).

• ROS Documentation

Example:

#include <eigen_conversions/eigen_msg.h>

Eigen::Vector3d my_super_cool_vector(1.0, 2.0, 3.0);
geometry_msgs::Point point_msg;
tf::pointEigenToMsg(my_super_cool_vector, point_msg);
super_cool_publisher_.publish(point_msg);

TF

To go to/from TF, use tf_conversions (or also minkindr_conversions below).

• ROS Documentation

Example:

#include <tf_conversions/tf_eigen.h>

Eigen::Vector3d my_super_cool_vector(1.0, 2.0, 3.0);
tf::Vector3 my_super_cool_vector_tf;
tf::vectorEigenToTF(my_super_cool_vector, my_super_cool_vector_tf);
tf::Transform transform;
transform.setOrigin(my_super_cool_vector_tf);
transform_broadcaster_.sendTransform(
    tf::StampedTransform(transform, ros::Time::now(), "map", "world"));

minkindr (aslam::Transformation)

Please use the minkindr_conversions package in the minkindr_ros repo. This also wraps some of the Eigen/TF conversions for common datatypes (Eigen::Quaterniond, Eigen::Vector3d), so it is a viable alternative to {tf,eigen}_conversions in most cases. It also transforms minkindr Transformations back and forth to both messages and TF.

• Code Documentation - Message

• Code Documentation - TF

Example:

#include <minkindr_conversions/kindr_msg.h>
#include <minkindr_conversions/kindr_tf.h>

Eigen::Quaterniond rotation(Eigen::Vector4d::Random());
rotation.normalize();
Eigen::Vector3d position(Eigen::Vector3d::Random());
kindr::minimal::QuatTransformation kindr_transform(rotation, position);

geometry_msgs::Pose msg;
tf::poseKindrToMsg(kindr_transform, &msg);
publisher_.publish(msg);

tf::Transform tf_transform;
tf::transformKindrToTF(kindr_transform, &tf_transform);
transform_broadcaster_.sendTransform(
    tf::StampedTransform(tf_transform, ros::Time::now(), "map", "world"));

OpenCV Image

Please use cv_bridge. This allows very easy conversions to/from ROS messages.

• ROS Tutorial

• ROS Documentation

Example:

#include <cv_bridge/cv_bridge.h>

const stereo_msgs::DisparityImageConstPtr& msg;  // We got this from a subscription callback.
cv::Mat output_image;
cv_bridge::CvImageConstPtr cv_img_ptr = cv_bridge::toCvShare(msg->image, msg);
// This is a shallow copy.
output_image = cv_img_ptr->image;

cv_bridge::CvImage image_cv_bridge;
image_cv_bridge.header.frame_id = "map";
image_cv_bridge.image = output_image;
publisher_.publish(image_cv_bridge.toImageMsg());