README

ROS Apriltag drawing package

This repository has a ROS2 component for drawing apriltags onto an image. You will find this package handy when trouble shooting apriltag detection problems. The node in this package is usually launched from a launch file in the apriltag_detector package. Refer there for more information.

Components

apriltag_draw::ApriltagDraw

Topics (subscribed):
- tags: the detected tags from the apriltag library.
- image: the image from which the tags were detected. Must be synced with tags, i.e. identical header time stamps in both streams.
Topics (published):
- image_tags: image with the tags drawn onto
Parameters:
- image_transport: What image transport to use (default raw)
- qos_profile: What profile to use for subscribing to images. Allowed are sensor_data and default. Default default.
- max_queue_size: How many images or tag detections to keep. Default: 200.

Launch files

draw.launch.py

Arguments:

camera: name of the camera, e.g. /camera_0. Default: camera.
image: name of the image underneath the camera node, e.g. image_raw. The node will then subscribe to images /camera_name/image_raw. Default: image_raw.
image_transport: the transport to use, e.g. compressed, ffmpeg etc. Default: raw.

composable.launch.py

This launch script has identical arguments to draw.launch.py, but is implemented as a composable node for illustration purposes.

Example usage

ros2 launch apriltag_draw draw.launch.py  image_transport:=ffmpeg camera:=/cam_sync/cam3

Will create a node using the compressed ffmpeg image transport, using the following topics, and publishing an image under /cam_sync/cam3/tags.

 Subscribers:
    /cam_sync/cam3/image_raw/ffmpeg: ffmpeg_image_transport_msgs/msg/FFMPEGPacket
    /cam_sync/cam3/tags: apriltag_msgs/msg/AprilTagDetectionArray
  Publishers:
    /cam_sync/cam3/image_tags: sensor_msgs/msg/Image
    /cam_sync/cam3/image_tags/ffmpeg: ffmpeg_image_transport_msgs/msg/FFMPEGPacket

License

This software is issued under the Apache License Version 2.0.