Image Segmentation

Description

Image Segmentation is a ROS package that transforms the 3D coordinates of pointcloud clusters to pixels and cuts an image that depicts the object of the specific cluster for every one of them, out of the equivalent camera frame.

The purpose of this demo is to showcase the image segmentation of a specific cluster, in our case, a person.

Files Included:

1. image_segmentation_node: This is the node that subscribes to the output topic of pointcloud2_cluster_tracking. It calculates the angle-to-pixel transformation and cuts an image out of the latest camera frame for every cluster for every instance of the pointcloud.
2. seg_listener: This is a node that subscribes to the output topic of image_segmentation_node. It saves the segmented images in the current directory as .png files.

Topics

• seg_images: on which image_segmentation_node publishes messages of image_msgs::Image_Segments type. seg_listener subscribes to this topic.
• image_segmentation_node/seg_image: on which image_segmentation_node publishes the cropped images that correspond to a cluster with a specific ID.
• test_pcl: on which image_segmentation_node publishes the pointcloud of a cluster with a specific ID.

Dependencies

This package is dependent on the following ROS packages:

• Laserscan Stacker
• Pointcloud2 Clustering
• Pointcloud2 Cluster Tracking
• PointCloud2 Segments Viz
• Pointcloud msgs
• Image msgs
• hpr

The package also requires the OpenCV library, which is included and automatically installed during the ROS installation process.

Instructions

To run the demo, follow these steps:

1. First of all, you need to download and install Git LFS on your system in order to download the rosbags for the demo. You can follow the instructions here: https://github.com/git-lfs/git-lfs

2. Create a ROS workspace (let's assume it's named catkin_ws) and open a terminal inside the src directory of the workspace.

3. Clone all necessary packages from GitHub using the following commands:
   git clone https://github.com/roboskel/pointcloud_msgs.git
git clone https://github.com/roboskel/laserscan_stacker.git
git clone https://github.com/roboskel/pointcloud2_clustering.git
git clone https://github.com/roboskel/pointcloud2_cluster_tracking.git
git clone https://github.com/roboskel/pointcloud2_segments_viz.git
git clone https://github.com/roboskel/hpr.git
git clone https://github.com/roboskel/image_segmentation_node.git
git clone https://github.com/roboskel/image_msgs.git

4. Run cd hpr. Switch to rel3 branch by running git checkout rel3

5. If you want to change the value of the safety_pixels parameter (defines the number of extra pixels added to each side of the cropped images), go to src/image_segmentation_node/src and open image_segmentation.cpp. In main function, change the following line:
   nh.param<int>("safety_pixels", safety_pixels, 20);
   to
   nh.param<int>("safety_pixels", safety_pixels, <your_pixels>);, where <your_pixels> is an integer of your choice (>=0).
   There is also a parameters.yaml file, for passing values to the safety_pixels parameter (the creation of a launch file is needed in this case)

6. Go to src/hpr/launch and open hpr_test.launch file with a text editor. Change the following line: <param name="use_sim_time" value="False" />
   to
   <param name="use_sim_time" value="True" />

7. Go to src/laserscan_stacker/config/ and open laserscan_stacker.yaml file with a text editor. Change the input topic parameter value to /rear_cam/image_raw

8. Go to src/pointcloud2_cluster_tracking/config and open param.yaml with a text editor. Change method to 2.

9. Go to the root of your workspace directory and run catkin_make to build the packages.

10. Run roscore

11. In a new terminal, go to the rosbags directory, and run: rosbag play 1.bag --clock

12. In a new terminal, run roslaunch hpr hpr_test.launch

13. In a new terminal, run rosrun image_segmentation_node image_segmentation

14. In a new terminal, run rviz

15. If you want to save all segmented images to the disk, open a new terminal in the directory you want to save the images in and run rosrun image_segmentation_node seg_listener.

16. In rviz, follow these steps:

• In Global Options. change the fixed frame by selecting base link from the dropdown menu.
• Click on Add button, then click on the By topic tab.
• Select LaserScan under /hokuyo_base/scan and click OK
• In a similar fashion, add the following topics:
  • /image_segmentation_node/seg_image
  • /rear_cam/image_raw
  • /test_pcl
  • /pointcloud2_segments_viz/pc2_viz

16. Enjoy the demo!

This package was developed and tested for ROS Melodic.