Unable to detect AprilTag using ROS on Raspberry Pi

edit

Hi,

I'm running ROS indigo on a Raspberry Pi with IMX219 Raspberry Pi Camera V2. Yet I can’t seem to detect the AprilTag. The raw images and camera info are being published by raspicam_node. The code of the launch file for raspicam_node is:

<launch>

  <node pkg="raspicam" type="raspicam_raw_node" name="raspicam_node" respawn="true" ns="camera" output="screen">
    <param name="quality" type="double" value="10.0"/>
    <param name="framerate" type="double" value="50.0"/>
    <param name="width" type="double" value="320.0" />
    <param name="height" type="double" value="240.0" />
  </node>

  <!--node pkg="image_proc" type="image_proc" name="image_proc" respawn="true" ns="/camera"/-->
</launch>

The raw images and camera info are then subscribed by apriltag_detector. The code of the launch file for apriltag_detector is:

<?xml version="1.0" encoding="ISO-8859-15"?>

<launch>
  <node pkg="apriltags_ros" type="apriltag_detector_node" name="apriltag_detector" output="screen" ns="camera">
    <remap from="image_rect" to="image_raw" />
    <remap from="camera_info" to="camera_info" />

    <!-- Select the tag family: 16h5, 25h7, 25h9, 36h9, or 36h11(default) -->
    <param name="tag_family" type="str" value="36h11" />

    <!-- Enable projected optical measurements for more accurate tag transformations -->
    <!-- This exists for backwards compatability and should be left true for new setups -->
    <param name="projected_optics" type="bool" value="true" />

    <!-- Enter your AprilTag information below. Add all tag IDs that will be used, with their sizes -->
    <rosparam param="tag_descriptions">[
      {id: 0, size: 0.08, frame_name: tag_0},
      {id: 1, size: 0.08, frame_name: tag_1},
      {id: 2, size: 0.08, frame_name: tag_2},
      {id: 3, size: 0.08, frame_name: tag_3},
      {id: 4, size: 0.08, frame_name: tag_4},
      {id: 5, size: 0.08, frame_name: tag_5},
      {id: 6, size: 0.08, frame_name: tag_6},
      {id: 7, size: 0.08, frame_name: tag_7},
      {id: 8, size: 0.08, frame_name: tag_8},
      {id: 9, size: 0.08, frame_name: tag_9},
      {id: 10, size: 0.08, frame_name: tag_10},
      {id: 11, size: 0.08, frame_name: tag_11},
      {id: 12, size: 0.08, frame_name: tag_12},
      {id: 13, size: 0.08, frame_name: tag_13},
      {id: 14, size: 0.08, frame_name: tag_14},
      {id: 15, size: 0.08, frame_name: tag_15},
      ]
    </rosparam>
  </node>
</launch>

I have tried the following measures to debug this issue, but with no luck:

1. Adjust the camera focal length to make sure the images are reasonably focused.
2. Recalibrate the camera using rosrun camera_calibration cameracalibrator.py
3. Feed an original tag image directely to the apriltag_detector node.

Any idea what should I do to debug this issue? I am new to ROS, so any help would be greatly appreciated.