cameracalibrator fails for mono image in ROS 2 Humble.

[TannerGilbert]

I have a camera that publishes images in mono8:

ros_image = self.bridge.cv2_to_imgmsg(arr, encoding="mono8")
ros_image.header.stamp = self.get_clock().now().to_msg()
ros_image.header.frame_id = self.frame_id
self.publisher_.publish(ros_image)

I wanted to do the calibration with cameracalibrator but when running ros2 run camera_calibration cameracalibrator --size 8x10 --square 0.015 --ros-args -r image:=/camera/image_raw I get the following output:

Waiting for service camera/set_camera_info ...
OK
Waiting for service left_camera/set_camera_info ...
OK
Waiting for service right_camera/set_camera_info ...
OK
[WARN] [1744132236.138276860] [cameracalibrator]: No publishers available for topic /left. Using system default QoS for subscriber.
[WARN] [1744132236.140784587] [cameracalibrator]: No publishers available for topic /right. Using system default QoS for subscriber.
Exception in thread Thread-1:
TypeError: unknown is not a numpy array, neither a scalar

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/usr/lib/python3.10/threading.py", line 1016, in _bootstrap_inner
    self.run()
  File "/home/sapience/sapience_ws/build/camera_calibration/src/camera_calibration/camera_calibrator.py", line 91, in run
    self.function(m)
  File "/home/sapience/sapience_ws/build/camera_calibration/src/camera_calibration/camera_calibrator.py", line 175, in handle_monocular
    drawable = self.c.handle_msg(msg)
  File "/home/sapience/sapience_ws/build/camera_calibration/src/camera_calibration/calibrator.py", line 958, in handle_msg
    gray = self.mkgray(msg)
  File "/home/sapience/sapience_ws/build/camera_calibration/src/camera_calibration/calibrator.py", line 378, in mkgray
    return self.br.imgmsg_to_cv2(msg, "mono8")
  File "/home/sapience/sapience_ws/install/cv_bridge/local/lib/python3.10/dist-packages/cv_bridge/core.py", line 194, in imgmsg_to_cv2
    res = cvtColor2(im, img_msg.encoding, desired_encoding)
SystemError: <Boost.Python.function object at 0xaaaacaeb7ed0> returned a result with an exception set

In calibrator.py it correctly detects that the image is mono8 (

image_pipeline/camera_calibration/src/camera_calibration/calibrator.py

Line 378 in b381f6a

return self.br.imgmsg_to_cv2(msg, "mono8")

) but then cvtColor2 fails in the cv_bridge (https://github.com/ros-perception/vision_opencv/blob/27de9ecf9862e6fba509b7e49e3c2511c7d11627/cv_bridge/src/module.cpp#L42). Note cv_bridge was also build from source with the Humble branch.