image_view: consistent image_transport (#876)

All of these nodes already have the proper remapping support - but
image_transport parameter support was scattered

image_view/src/extract_images_node.cpp

@@ -75,13 +75,15 @@ ExtractImagesNode::ExtractImagesNode(const rclcpp::NodeOptions & options)
   auto node_base = this->get_node_base_interface();
   std::string topic = node_base->resolve_topic_or_service_name("image", false);
 
-  this->declare_parameter<std::string>("transport", std::string("raw"));
+  // TransportHints does not actually declare the parameter
+  this->declare_parameter<std::string>("image_transport", "raw");
+  image_transport::TransportHints hints(this);
   std::string transport = this->get_parameter("transport").as_string();
 
   sub_ = image_transport::create_subscription(
     this, topic, std::bind(
       &ExtractImagesNode::image_cb, this, std::placeholders::_1),
-    transport);
+    hints.getTransport());
 
   auto topics = this->get_topic_names_and_types();
 

image_view/src/image_saver_node.cpp

@@ -71,6 +71,10 @@ namespace image_view
 ImageSaverNode::ImageSaverNode(const rclcpp::NodeOptions & options)
 : rclcpp::Node("image_saver_node", options)
 {
+  // TransportHints does not actually declare the parameter
+  this->declare_parameter<std::string>("image_transport", "raw");
+  image_transport::TransportHints hints(this);
+
   // For compressed topics to remap appropriately, we need to pass a
   // fully expanded and remapped topic name to image_transport
   auto node_base = this->get_node_base_interface();
@@ -80,13 +84,13 @@ ImageSaverNode::ImageSaverNode(const rclcpp::NodeOptions & options)
   cam_sub_ = image_transport::create_camera_subscription(
     this, topic, std::bind(
       &ImageSaverNode::callbackWithCameraInfo, this, std::placeholders::_1, std::placeholders::_2),
-    "raw");
+    hints.getTransport());
 
   // Useful when CameraInfo is not being published
   image_sub_ = image_transport::create_subscription(
     this, topic, std::bind(
       &ImageSaverNode::callbackWithoutCameraInfo, this, std::placeholders::_1),
-    "raw");
+    hints.getTransport());
 
   std::string format_string;
   format_string = this->declare_parameter("filename_format", std::string("left%04i.%s"));

image_view/src/image_view_node.cpp

@@ -104,15 +104,16 @@ cv_bridge::CvImageConstPtr ThreadSafeImage::pop()
 ImageViewNode::ImageViewNode(const rclcpp::NodeOptions & options)
 : rclcpp::Node("image_view_node", options)
 {
-  auto transport = this->declare_parameter("image_transport", "raw");
-  RCLCPP_INFO(this->get_logger(), "Using transport \"%s\"", transport.c_str());
+  // TransportHints does not actually declare the parameter
+  this->declare_parameter<std::string>("image_transport", "raw");
+  image_transport::TransportHints hints(this);
+  RCLCPP_INFO(this->get_logger(), "Using transport \"%s\"", hints.getTransport().c_str());
 
   // For compressed topics to remap appropriately, we need to pass a
   // fully expanded and remapped topic name to image_transport
   auto node_base = this->get_node_base_interface();
   std::string topic = node_base->resolve_topic_or_service_name("image", false);
 
-  image_transport::TransportHints hints(this, transport);
   pub_ = this->create_publisher<sensor_msgs::msg::Image>("output", 1);
   sub_ = image_transport::create_subscription(
     this, topic, std::bind(

image_view/src/stereo_view_node.cpp

@@ -97,8 +97,9 @@ StereoViewNode::StereoViewNode(const rclcpp::NodeOptions & options)
   std::string format_string = this->get_parameter("filename_format").as_string();
   filename_format_.parse(format_string);
 
-  this->declare_parameter<std::string>("transport", std::string("raw"));
-  std::string transport = this->get_parameter("transport").as_string();
+  // TransportHints does not actually declare the parameter
+  this->declare_parameter<std::string>("image_transport", std::string("raw"));
+  image_transport::TransportHints hints(this);
 
   // Do GUI window setup
   int flags = autosize ? (cv::WINDOW_AUTOSIZE | cv::WINDOW_KEEPRATIO | cv::WINDOW_GUI_EXPANDED) : 0;
@@ -126,8 +127,8 @@ StereoViewNode::StereoViewNode(const rclcpp::NodeOptions & options)
     stereo_ns + "/disparity", this->get_name(), this->get_namespace());
 
   // Subscribe to three input topics.
-  left_sub_.subscribe(this, left_topic, transport);
-  right_sub_.subscribe(this, right_topic, transport);
+  left_sub_.subscribe(this, left_topic, hints.getTransport());
+  right_sub_.subscribe(this, right_topic, hints.getTransport());
   disparity_sub_.subscribe(this, disparity_topic);
 
   RCLCPP_INFO(

image_view/src/video_recorder_node.cpp

@@ -66,13 +66,19 @@ VideoRecorderNode::VideoRecorderNode(const rclcpp::NodeOptions & options)
     rclcpp::shutdown();
   }
 
+  // TransportHints does not actually declare the parameter
+  this->declare_parameter<std::string>("image_transport", "raw");
+  image_transport::TransportHints hints(this);
+
   // For compressed topics to remap appropriately, we need to pass a
   // fully expanded and remapped topic name to image_transport
   auto node_base = this->get_node_base_interface();
   std::string topic = node_base->resolve_topic_or_service_name("image", false);
 
   sub_image = image_transport::create_subscription(
-    this, topic, std::bind(&VideoRecorderNode::callback, this, std::placeholders::_1), "raw");
+    this, topic, std::bind(
+      &VideoRecorderNode::callback, this,
+      std::placeholders::_1), hints.getTransport());
 
   RCLCPP_INFO(this->get_logger(), "Waiting for topic %s...", topic.c_str());
 }