Objectives

Computer vision is an important part of how a robot perceives the world around itself. In this lab you will create a color filtering node to detect one of several colored spheres. Specifically:

1. Subscribe to the input image topic. This is likely from the image_publisher node (see below) but you may remap as you wish.
2. Publish a filtered image that shows JUST the colored sphere. Images of the given ping pong balls are here:
   1. Blue ping-pong ball
   2. Pink ping-pong ball
3. Use some method to easily switch between color filters to change which sphere is being found (a parameter is probably a good choice). Do NOT write multiple color filtering nodes.
   NOTE: each color should only have ONE set of filters regardless of lighting conditions
4. Once you do the above, find something spherical (or, at least something that presents a circle to the camera) in a NEW color, record your own images with the method of your choice, and create a third filter to find this object.
5. Demonstrate the above and answer questions.

Tips

• ROS2 contains a node to publish and a node to view images easily:
  • Publish as /image_raw:

     $ ros2 run image_publisher image_publisher_node <path/to/image.png>

  • View topic of choice:

     $ ros2 run image_view image_view --ros-args --remap image:=<YOUR_TOPIC>

• Create a launch file that starts your filtering node and image view to save time
• Get rid of some of the noise by using erode and dilate. MAKE SURE YOU ERODE AND DILATE THE SAME NUMBER OF TIMES TO KEEP THE OBJECT THE SAME SIZE!
• Do Lab 3.2 immediately after finishing this one for the smoothest results.
• Unzip the above images and put them somewhere in your src folder to make them accessible to your container.

Submission Instructions

Submit a PDF to blackboard with:

1. Your git repo URL and git tag for this assignment.
2. The color ranges to filter each object
3. Any difficulties you had with this assignment.

Rubric

• Demonstration: 30 points
  • Filtered image shown: 5 points
  • Filters only the object:
    • Blue ping pong: 5 points
    • Pink ping pong: 5 points
    • Third object: 5 points
  • Answers questions about code: 10 points
• Blackboard submission: 10 points