• ROS2 (DISTRO: galactic) installed and sourced

• YOLOv5 requirements satisfied

• ROS usb_cam installed

  sudo apt-get install ros-{ROS2_DISTRO}-usb-cam

• source ros2

  source /opt/ros/galactic/setup.bash

  use command echo ${ROS_DISTRO} to make sure your current Terminal is sourced to a ROS2 distro, e.g. galactic

• compile the workspace first

  cd ros2_yolov5_webcam/colcon_ws
  colcon build

• copy the folder /data in

  /src/yolov5_detect/yolov5/

  to

  /install/yolov5_detect/lib/python3.8/site-packages/yolov5/

• make sure to set device-id as 0 in webcam_yolo_pub.py:

  self.cap = cv2.VideoCapture(0)

• launch the nodes

  # stay in the /colcon_ws directory
  source install/setup.sh
  ros2 launch yolov5_detect yolo_webcam_detect.launch.py

• to friends who comes from the SONY setup project: make sure to set device-id as 2 in webcam_yolo_pub.py:

  self.cap = cv2.VideoCapture(2)

  to whom who has interest in using an external SONY camera as a substitution of web-camera:
  SONY a7r4 setup for Ubuntu

  # stay in the /colcon_ws directory
  source install/setup.sh
  ros2 launch yolov5_detect yolo_sony_detect.launch.py

below are some notes during development...

To learning how to build a ros node containing a custom submodule, check these blogs on ROS answer:

• Including a Python module in a ROS2 package
• ROS2 Python relative import of my scritps
• All google searching results...

How did I do:

the following guide just works, but not so elegant...*

Capsule the detect as a class Yolov5Detector(), which would be easier to be implemented in ros node script.
The yolov5 folder is placed directly in our package folder, parallel with sub-package folder:

colcon_ws
├── src
│   ├── yolov5_detect #------------------------ROS package folder
│   │   ├── package.xml
│   │   ├── setup.py
│   │   ├── setup.cfg
│   │   ├── yolov5_detect #----------------ROS package sub-folder
│   │   │   ├── __init__.py
│   │   │   ├── webcam_yolo_sub.py #------------- ROS node script
│   │   │   └── ...
│   │   │
│   │   └── yolov5 #-------------------------the yolov5 submodule
│   │       └── ...
│   │
│   ├── install
│   ├── build
│   └── log
│
└── README.md

Declare the submodule names in setup.py to ensure them to be compiled together into /install after colcon build:

from setuptools import setup
from setuptools import find_packages

package_name = 'yolov5_detect'
submodules = 'yolov5_detect/yolov5'  # declare the submodule to be build

setup(
    name=package_name,
    version='0.0.0',
    packages=find_packages(),
    include_package_data=True,
    data_files=[
        ('share/ament_index/resource_index/packages',
            ['resource/' + package_name]),
        ('share/' + package_name, ['package.xml']),
        ################## MODIFIED ##################
        (os.path.join('share', package_name, 'launch'),
         glob(os.path.join('launch', '*.launch.py'))),
        (os.path.join('share', package_name, 'yolov5'),
         glob(os.path.join('yolov5', '*.*'))),
        ################## MODIFIED ##################
        # this part helps copy the necessary files into /install directory
    ],
    install_requires=['setuptools'],
    zip_safe=True,
    maintainer='jun',
    maintainer_email='[email protected]',
    description='TODO: Package description',
    license='TODO: License declaration',
    tests_require=['pytest'],
    entry_points={
        'console_scripts': [  # define the entry_points as usual
            'webcam_yolo_pub=yolov5_detect.webcam_yolo_pub:main',
            'webcam_yolo_sub=yolov5_detect.webcam_yolo_sub:main'
        ],
    },
)

To connect the scripts from yolov5's subfolders like utils and models correctly, we need to switch the relative path to absolute path, i.e. add yolov5. ahead of the folder names in ALL relevant scripts:

from utils.plots import Annotator, colors, save_one_box

# --> MODIFY: add '<submodule_name>. ahead

from yolov5.utils.plots import Annotator, colors, save_one_box

Here I managed to do it via running the node again and again and allocate ALL the relevant scripts in the error messages.

copy the folder /data containing .yaml files in

/src/yolov5_detect/yolov5/

to

/install/yolov5_detect/lib/python3.8/site-packages/yolov5/