[ros2] Port multicamera to ros2

[shiveshkhaitan]

Port gazebo_ros_multicamera plugin to ROS2.

Example:

<plugin name="camera_controller" filename="libgazebo_ros_camera.so">
  <ros>
      <namespace>demo_cam</namespace>
      <!-- topics need to be prefixed with camera_name for remapping -->
      <argument>mycamera/left/image_raw:=mycamera/left/image_demo</argument>
      <argument>mycamera/right/image_raw:=mycamera/right/image_demo</argument>
       <argument>mycamera/left/camera_info:=mycamera/left/camera_info_demo</argument>
       <argument>mycamera/right/camera_info:=mycamera/right/camera_info_demo</argument>
    </ros>

  <camera_name>mycamera</camera_name>
  <sensor_type>2</sensor_type>
  <!-- frame_name>omit so it defaults to link name</frameName-->
</plugin>

Instead of a new plugin, multicamera has been integrated into gazebo_ros_camera. To use it as multicamera, <sensor_type> has to be specified as 2. It also includes gazebo_ros_triggered_multicamera

[chapulina]

Now that #932 has been merged, this needs rebasing

[chapulina]

Works for me! The requests for changes are minimal, the only critical one is changing the plugin namespace.

[chapulina]

Can we put this plugin in the gazebo_plugins namespace? Just in case someone creates the same plugin for Gazebo in the future.

In fact, feel free to make a pull request adding this plugin to Gazebo 9 if you have time. It would be just a matter of copying this and the cc file over, and making a couple tweaks to follow Gazebo's style guide (which is different from ROS 2).

I can help you out with style changes for you since I'm used to it. Some things I can already see:

• rename .hpp to .hh and .cpp to .cc
• Use camelCase (i.e. cameraNum)
• Prefix all arguments with _ (i.e. _cameraNum)
• There should be one public / protected / private per member
• { in a new line

The only problem is that even if we release this plugin for Gazebo 9.X, it won't be available to most ROS users, which use Gazebo 9.0.0 from Ubuntu. So we woudn't be able to use it in gazebo_ros_pkgs's debian packages 😕

[shiveshkhaitan]

I will be making the PR soon

[chapulina]

LGTM. We could backport this to dashing.