What Is This?

The demos in this package are designed to showcase how developers can manually compose ROS 2 nodes by defining them separately but combining them in varied process layouts.

These can be done while avoiding code overhauls or performance restrictions.

This package consists of the following ROS 2 nodes:

1. camera_node
2. watermark_node
3. image_view_node
4. image_pipeline_all_in_one
5. two_node_pipeline
6. cyclic_pipeline
7. image_pipeline_with_two_image_view

Through the use of intra-process (as opposed to inter-process) node communication, lower latency and thus higher efficiency is observed for ROS 2 topologies that utilizes this manner of communication.

The improvements in latency reduction are even more pronounced when applied to ROS 2 systems with more complex topologies.

Build

colcon build --packages-up-to intra_process_demo

Run

1. Two Node Pipeline

Run two_node_pipeline via the commands below:

ros2 run intra_process_demo two_node_pipeline

This sets up two nodes, a ROS 2 node that publishes a string with an incremeting integer value, as well as a ROS 2 node that subscribes to print the received string.

2. Cyclic Pipeline

Run cyclic_pipeline via the commands below:

ros2 run intra_process_demo cyclic_pipeline

Similar to the previous, instead of creating a new message for each new iteration, the publisher and subscriber nodes only ever use one message instance. This is achieved by having a cycle in the graph and kickstarting the communication externally by having one of the nodes publish before spinning the executor.

3. Image Pipeline All In One

Please ensure you have a camera connected to your workstation.

image_pipeline_all_in_one consists of 3 nodes, where camera_node publishes a unique_ptr message onto the topic, \image. Subsequently, watermark_node subscribes to the previous, republishes the image after adding a watermark on the topic, \watermarked_image, and the final node, image_view_node, subscribes to this last topic in order to display it for user.

ros2 run intra_process_demo image_pipeline_all_in_one

4. Image Pipeline All Separately

Please ensure you have a camera connected to your workstation.

In direct contrast with the previous, run the following commands in separate terminals to have camera_node, watermark_node and image_view_node all in their own process, utilizing inter-process node communication.

This starts the camera_node ROS 2 node and publishes images captured from your workstation web camera onto a ROS 2 topic labelled /image.

# Open new terminal
ros2 run intra_process_demo camera_node

This starts the watermark_node ROS 2 node which subscribes to raw images from ROS 2 topic /image, overlays both process ID number and message address on top of the image visually and publishes to ROS 2 topic /watermarked_image.

# Open new terminal
ros2 run intra_process_demo watermark_node

This starts the image_view_node ROS 2 node which subscribes to /watermarked_image and displays the received images in an OpenCV GUI window.

# Open new terminal
ros2 run intra_process_demo image_view_node

5. Image Pipeline With Two Image Views

Please ensure you have a camera connected to your workstation.

Similar to the Image Pipeline All In One, running image_pipeline_with_two_image_view will display the image process through intra-process communications.

However, it now instantiates 2 image_view_node ROS 2 nodes.

# Open new terminal
ros2 run intra_process_demo image_pipeline_with_two_image_view

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Changelog for package intra_process_demo

0.27.2 (2024-07-10)

• Removed pre-compiler check for opencv3 (#698)
• Fix executable name in README.md (#692)
• Contributors: Alejandro Hernández Cordero, Trushant Adeshara

0.27.1 (2023-05-11)

• Fix executable name in README (#619)
• Contributors: Yadunund

0.27.0 (2023-04-13)

• Change all ROS2 -> ROS 2. (#610)
• Contributors: Chris Lalancette

0.26.0 (2023-04-11)

• Added README.md for intra_process_demo (#595)
• Contributors: Gary Bey

0.25.0 (2023-03-01)

0.24.1 (2023-02-24)

0.24.0 (2023-02-14)

• Update the demos to C++17. (#594)
• [rolling] Update maintainers - 2022-11-07 (#589)
• Contributors: Audrow Nash, Chris Lalancette

0.23.0 (2022-11-02)

0.22.0 (2022-09-13)

0.21.0 (2022-04-29)

0.20.1 (2022-04-08)

0.20.0 (2022-03-01)

• Add opencv_imgproc dependency for cv::putText (#554)
• Install includes to include/${PROJECT_NAME} (#548)
• Contributors: Shane Loretz

0.19.0 (2022-01-14)

• Fix include order and relative paths for cpplint (#551)
• Contributors: Jacob Perron

0.18.0 (2021-12-17)

• Update maintainers to Audrow Nash and Michael Jeronimo (#543)
• Additional fixes for documentation in demos. (#538)
• Contributors: Audrow Nash, Chris Lalancette

0.17.0 (2021-10-18)

• Fixing deprecated subscriber callback warnings (#532)
• Contributors: Abrar Rahman Protyasha

0.16.0 (2021-08-11)

• Revert "Add type masquerading demos (#482)" (#520)
• Add type masquerading demos (#482)
• Contributors: Audrow Nash, William Woodall

0.15.0 (2021-05-14)

0.14.2 (2021-04-26)

0.14.1 (2021-04-19)

0.14.0 (2021-04-06)

0.13.0 (2021-03-25)

0.12.1 (2021-03-18)

0.12.0 (2021-01-25)

0.11.0 (2020-12-10)

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