Tutorials

Launching stereo_image_proc Components

While each of the components is available as a ROS 2 node, the recommended way to build pipelines is using the components as this will save overhead by not having to serialize messages between components.

For a detailed example, see stereo_image_proc.launch.py.

Using Compressed Image Transport

All of the components and nodes in stereo_image_proc support image_transport. This allows a subscriber to specify the transport to be used. By default, this is raw, which means an uncompressed sensor_msgs/Image. When transmitting images over limited bandwidth networks, such as WiFi, it can be helpful to use compressed format.

$ ros2 run stereo_image_proc disparity_node --ros-args -p image_transport:=compressed

Remapping camera_info Topics

When a camera_info topic is needed, an image_transport camera subscriber is typically used. ROS 2 convention for naming camera_info topics is:

• camera/image - an image in namespace camera.

• camera/camera_info - the associated camera info

So if a node subscribes to a topic called image, and the user remaps this to my_camera/image, then the associated camera info will be automatically remapped to mycamera/camera_info.

Most ROS 2 camera drivers will follow the convention, but occasionally they do not. In this case, you will have to manually remap the camera_info - but due to the way that ROS 2 remapping works you have to use the fully resolved camera info topic. An example:

• image is remapped to my_camera/image.

• The fully resolved name for the camera info is now my_camera/camera_info.

• If your camera driver actually publishes another_ns/camera_info, then you would have to remap my_camera/camera_info to another_ns/camera_info.