ROSTopic.publish#

ROSTopic.publish(msg: dict | Image | PointCloud, timestamp_ns: int | None = None) → None[source]#

Publish a message on the configured ROS topic.

Parameters:

  • msg (dict, Image, or PointCloud) – ROS payload as a message dictionary, Image, or PointCloud

  • timestamp_ns (int or None) – optional timestamp in nanoseconds since Unix epoch; used for generated ROS headers. If None, message/object timestamp is used when present, otherwise current wall-clock time is used.

Dictionary payloads are forwarded directly and must match the configured ROS message type.

If msg is an Image, it is serialised according to the configured topic message type:

  • sensor_msgs/Image or sensor_msgs/msg/Image for raw image data

  • sensor_msgs/CompressedImage or sensor_msgs/msg/CompressedImage for JPEG-compressed image data

Colour plane order is encoded in the ROS encoding field for raw images, and in the compressed-message format string for compressed images.

If msg is a PointCloud, it is published as sensor_msgs/PointCloud2 with x, y, z fields and an rgb field when colour data is present.

Example publishing a std_msgs/String message:

pub = ROSTopic("/cmd_text", message="std_msgs/String", subscribe=False)
pub.publish({"data": "hello"})
pub.release()

Example publishing a geometry_msgs/Twist message:

pub = ROSTopic("/cmd_vel", message="geometry_msgs/Twist", subscribe=False)
pub.publish(
    {
        "linear": {"x": 0.2, "y": 0.0, "z": 0.0},
        "angular": {"x": 0.0, "y": 0.0, "z": 0.5},
    }
)
pub.release()

Example publishing an Image with an explicit timestamp:

img = Image(np.zeros((240, 320, 3), dtype=np.uint8), colororder="RGB")
pub = ROSTopic("/camera/image_raw", message="sensor_msgs/Image", subscribe=False)
pub.publish(img, timestamp_ns=1_700_000_000_123_456_789)
pub.release()

Example publishing a PointCloud with an explicit timestamp:

points = np.array([[0.0, 1.0], [0.0, 0.2], [1.0, 1.2]], dtype=np.float32)
pc = PointCloud(points)
pub = ROSTopic("/cloud", message="sensor_msgs/PointCloud2", subscribe=False)
pub.publish(pc, timestamp_ns=1_700_000_000_223_456_789)
pub.release()

The topic is advertised lazily on first publish.