checkerboard_detector

checkerboard_detector is an executabel to detect checker board. You can find marker patter in jsk-ros-pkg/calibboard_sheet.

Subscribing Topics

  • ~image (sensor_msgs/Image)

  • ~camera_info (sensor_msgs/CameraInfo)

    Input image and camera info. Intrinsic camera parameter is acquired from ~camera_info.

Publishing Topics

  • ObjectDetection (posedetection_msgs/ObjectDetection)

  • objectdetection_pose (geometry_msgs/PoseStamped)

    Pose of checkerboard in posedetection_msgs/ObjectDetection and geometry_msgs/PoseStamped.

  • corner_point (geometry_msgs/PointStamped)

    Corner points.

  • polygons (jsk_recognition_msgs/PolygonArray)

    Publish checker board as jsk_recognition_msgs/PolygonArray. It is useful to visualize in rviz.

Parameters

  • display (default: 0)

    Set 1 to enable debug view.

  • board_type (default: chess)

    Type of marker. chess, circle and acircle are supported.

  • rect%d_size_x

  • rect%d_size_y

    Size of checkerboard in m unit.

  • grid%d_size_x

  • grid%d_size_y

    The number of grids in x and y axis.

  • use_P (default: false)

    By default, use camera matrix (K) and unrectified image (image_raw). If you use rectified image (image_rect), use_P should be true.

  • invert_color (default: false)

    Invert white and black before searching cross points or circles.

  • message_throttle (default: 1)

    Finding checker boards every message_throttle images

  • queue_size (default: 1)

  • publish_queue_size (default: 1)

    Size of queue of subscriber is queue_size, publisher is publish_queue_size.

  • axis_size (default: 0.05)

  • circle_size (default: 6)

    For setting displayed marker size. Set circle_size as [pixel]. Set axis_size as [m].

Trouble Shooting

  • Q. Estimated checker board pose is not correct

    A. First check debug image and all the detected corner points correctly superimposed on camera view.

    • If the detected corner points is not correct, you need to modify checker board grid size (grid_size parameters).
    • If the detected corner points is correct, confirm checker board size (rect_size parmaeters) and intrinsic camera paramter is calibrated well.
  • Q. How many number of grids better?

    A. I strongly recomment to choose oddxeven or evenxodd. Because if you choose oddxodd or evenxeven, detector will have two potential poses.