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https://github.com/christianrauch/apriltag_ros
ROS2 node for AprilTag detection
https://github.com/christianrauch/apriltag_ros
apriltag ros2
Last synced: 3 months ago
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ROS2 node for AprilTag detection
- Host: GitHub
- URL: https://github.com/christianrauch/apriltag_ros
- Owner: christianrauch
- License: mit
- Created: 2017-10-09T00:52:02.000Z (about 7 years ago)
- Default Branch: master
- Last Pushed: 2024-07-07T13:57:11.000Z (4 months ago)
- Last Synced: 2024-07-07T15:06:36.608Z (4 months ago)
- Topics: apriltag, ros2
- Language: C++
- Homepage:
- Size: 1.27 MB
- Stars: 128
- Watchers: 5
- Forks: 85
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# AprilTag ROS2 Node
This ROS2 node uses the AprilTag library to detect AprilTags in images and publish their pose, id and additional metadata.
For more information on AprilTag, the paper and the reference implementation: https://april.eecs.umich.edu/software/apriltag.html
## Topics
### Subscriptions:
The node subscribes via a `image_transport::CameraSubscriber` to rectified images on topic `image_rect`. The set of topic names depends on the type of image transport (parameter `image_transport`) selected (`raw` or `compressed`):
- `image_rect` (`raw`, type: `sensor_msgs/msg/Image`)
- `image_rect/compressed` (`compressed`, type: `sensor_msgs/msg/CompressedImage`)
- `camera_info` (type: `sensor_msgs/msg/CameraInfo`)
### Publisher:
- `/tf` (type: `tf2_msgs/msg/TFMessage`)
- `detections` (type: `apriltag_msgs/msg/AprilTagDetectionArray`)
The camera intrinsics `P` in `CameraInfo` are used to compute the marker tag pose `T` from the homography `H`. The image and the camera intrinsics need to have the same timestamp.
The tag poses are published on the standard TF topic `/tf` with the header set to the image header and `child_frame_id` set to either `tag:` (e.g. "tag36h11:0") or the frame name selected via configuration file. Additional information about detected tags is published as `AprilTagDetectionArray` message, which contains the original homography matrix, the `hamming` distance and the `decision_margin` of the detection.
## Configuration
The node is configured via a yaml configurations file. For the complete ROS yaml parameter file syntax, see: https://github.com/ros2/rcl/tree/master/rcl_yaml_param_parser.
The configuration file has the format:
```yaml
apriltag: # node name
ros__parameters:
# setup (defaults)
image_transport: raw # image format: "raw" or "compressed"
family: 36h11 # tag family name: 16h5, 25h9, 36h11
size: 1.0 # default tag edge size in meter
profile: false # print profiling information to stdout
# tuning of detection (defaults)
max_hamming: 0 # maximum allowed hamming distance (corrected bits)
detector:
threads: 1 # number of threads
decimate: 2.0 # decimate resolution for quad detection
blur: 0.0 # sigma of Gaussian blur for quad detection
refine: 1 # snap to strong gradients
sharpening: 0.25 # sharpening of decoded images
debug: 0 # write additional debugging images to current working directory
# (optional) list of tags
# If defined, 'frames' and 'sizes' must have the same length as 'ids'.
tag:
ids: [, , ...] # tag IDs for which to publish transform
frames: [, , ...] # frame names
sizes: [, , ...] # tag-specific edge size, overrides the default 'size'
```
The `family` (string) defines the tag family for the detector and must be one of `16h5`, `25h9`, `36h11`, `Circle21h7`, `Circle49h12`, `Custom48h12`, `Standard41h12`, `Standard52h13`. `size` (float) is the tag edge size in meters, assuming square markers.
Instead of publishing all tag poses, the list `tag.ids` can be used to only publish selected tag IDs. Each tag can have an associated child frame name in `tag.frames` and a tag specific size in `tag.sizes`. These lists must either have the same length as `tag.ids` or may be empty. In this case, a default frame name of the form `tag:` and the default tag edge size `size` will be used.
The remaining parameters are set to the their default values from the library. See `apriltag.h` for a more detailed description of their function.
See [tags_36h11.yaml](cfg/tags_36h11.yaml) for an example configuration that publishes specific tag poses of the 36h11 family.
## Nodes
### Standalone Executable
The `apriltag_node` executable can be launched with topic remappings and a configuration file:
```sh
ros2 run apriltag_ros apriltag_node --ros-args \
-r image_rect:=/camera/image \
-r camera_info:=/camera/camera_info \
--params-file `ros2 pkg prefix apriltag_ros`/share/apriltag_ros/cfg/tags_36h11.yaml
```
### Composable Node
For more efficient intraprocess communication, a composable node is provided:
```sh
$ ros2 component types
apriltag_ros
AprilTagNode
```
This `AprilTagNode` component can be loaded with other nodes into a "container node" process where they used shared-memory communication to prevent unnecessary data copies. The example launch file [v4l2_36h11.launch.yml](launch/v4l2_36h11.launch.yml) loads the `AprilTagNode` component together with the `v4l2_camera::V4L2Camera` component from the [`v4l2_camera` package](https://gitlab.com/boldhearts/ros2_v4l2_camera) (`sudo apt install ros-$ROS_DISTRO-v4l2-camera`) into one container and enables `use_intra_process_comms` for both:
```sh
ros2 launch apriltag_ros v4l2_36h11.launch.yml
```