snippet for image_tranpsort subscriber

src/image_transport_snippets.xml

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+<?xml version="1.0"?>
+<example>
+  <title>Image Transport Snippets</title>
+  <description>Collection of snippets for using image transport</description>
+  <ros_version>kinetic</ros_version>
+  <tag>cv_bridge</tag>
+  <tag>image_transport</tag>
+  <tag>image_geometry</tag>
+  <tag>roscpp</tag>
+  <time_limit>2</time_limit>
+  <language>
+    <name>cpp</name>
+    <run_cmd>rosrun image_transport_snippets camera_subscriber_snippet</run_cmd>
+    <start_file>src/camera_subscriber_snippet.cpp</start_file>
+  </language>
+  <feedback>
+    <tab>terminal</tab>
+  </feedback>
+  <feedback>
+    <tab>nodes</tab>
+  </feedback>
+</example>

src/image_transport_snippets/CMakeLists.txt

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+cmake_minimum_required(VERSION 2.8.3)
+project(image_transport_snippets)
+
+add_definitions(-std=c++11)
+find_package(catkin REQUIRED COMPONENTS
+  cv_bridge
+  image_transport
+  image_geometry
+  roscpp
+  tf2_ros
+)
+
+catkin_package(
+)
+
+include_directories(
+  ${catkin_INCLUDE_DIRS}
+)
+
+add_executable(camera_subscriber_snippet src/camera_subscriber_snippet.cpp)
+target_link_libraries(camera_subscriber_snippet ${catkin_LIBRARIES})
+
+## Install C++ Examples
+install(TARGETS camera_subscriber_snippet
+  ARCHIVE DESTINATION ${CATKIN_PACKAGE_LIB_DESTINATION}
+  LIBRARY DESTINATION ${CATKIN_PACKAGE_LIB_DESTINATION}
+  RUNTIME DESTINATION ${CATKIN_PACKAGE_BIN_DESTINATION}
+)
+
+## Install Other Resources
+install(DIRECTORY launch
+  DESTINATION ${CATKIN_PACKAGE_SHARE_DESTINATION})

src/image_transport_snippets/package.xml

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+<?xml version="1.0"?>
+<package format="2">
+  <name>image_transport_snippets</name>
+  <version>0.0.0</version>
+  <description>Code snippets for nodes using image_transport</description>
+
+  <maintainer email="st.fuchs.tr@gmail.com">Steffen Fuchs</maintainer>
+  <author email="st.fuchs.tr@gmail.com">Steffen Fuchs</author>
+  <license>BSD</license>
+
+
+  <buildtool_depend>catkin</buildtool_depend>
+
+  <depend>cv_bridge</depend>
+  <depend>image_transport</depend>
+  <depend>image_geometry</depend>
+  <depend>roscpp</depend>
+  <depend>tf2_ros</depend>
+
+</package>

src/image_transport_snippets/src/camera_subscriber_snippet.cpp

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+#include <ros/ros.h>
+#include <image_transport/image_transport.h>
+#include <image_geometry/pinhole_camera_model.h>
+#include <cv_bridge/cv_bridge.h>
+
+class CameraSubscriberNode
+{
+public:
+  CameraSubscriberNode(const ros::NodeHandle& nh=ros::NodeHandle(),
+                       const ros::NodeHandle& nh_private=ros::NodeHandle("~"))
+    : active_(false)
+    , nh_(nh)
+    , nh_priv_(nh_private)
+  {}
+
+  // We follow the design for managed nodes:
+  // http://design.ros2.org/articles/node_lifecycle.html
+  bool configure();
+  bool cleanup();
+  bool activate();
+  bool deactivate();
+
+  void imageCb(const sensor_msgs::ImageConstPtr& img_msg,
+               const sensor_msgs::CameraInfoConstPtr& info_msg);
+
+private:
+  bool active_;
+
+  ros::NodeHandle nh_;
+  ros::NodeHandle nh_priv_;
+  std::unique_ptr<image_transport::ImageTransport> it_;
+  image_transport::CameraSubscriber sub_img_;
+  image_transport::Publisher pub_img_;
+  image_geometry::PinholeCameraModel camera_model_;
+};
+
+// Definitions
+
+bool CameraSubscriberNode::configure()
+{
+  it_.reset( new image_transport::ImageTransport(nh_) );
+  sub_img_ = it_->subscribeCamera("image_input", 5, &CameraSubscriberNode::imageCb, this);
+  pub_img_ = it_->advertise("image_output", 1);
+
+  return true;
+}
+
+bool CameraSubscriberNode::cleanup()
+{
+  sub_img_.shutdown();
+  it_.reset();
+
+  return true;
+}
+
+bool CameraSubscriberNode::activate()
+{
+  return active_ = true;
+}
+
+bool CameraSubscriberNode::deactivate()
+{
+  return !(active_ = false);
+}
+
+void CameraSubscriberNode::imageCb(
+  const sensor_msgs::ImageConstPtr& img_msg,
+  const sensor_msgs::CameraInfoConstPtr& info_msg)
+{
+  if (!active_) return;
+
+  camera_model_.fromCameraInfo(info_msg);
+  // do somthing read only
+  const cv::Mat img = cv_bridge::toCvShare(img_msg)->image;
+  // ..
+
+  // modifiy the image
+  cv::Mat img_modified;
+  img.copyTo(img_modified);
+  pub_img_.publish(
+    cv_bridge::CvImage(
+      img_msg->header,
+      img_msg->encoding,
+      img_modified).toImageMsg());
+}
+
+
+int main(int argc, char** argv)
+{
+  ros::init(argc, argv, "camera_subscriber_node");
+  CameraSubscriberNode node;
+  // because there is no lifecycle manager, we need to trigger
+  // transitions manually
+  node.configure();
+  node.activate();
+  ros::spin();
+}