fiducial_marker

二维码 §

https://www.researchgate.net/publication/350418791_Fiducial_Markers_for_Pose_Estimation_Overview_Applications_and_Experimental_Comparison_of_the_ARTag_AprilTag_ArUco_and_STag_Markers

主流二维码的区别，选取，及使用技巧 §

• QR code的特点是其中三个角有“回”型定位点
• QR code主要用于储存更多的数据，定位稳定性比ArUco和AR Tag差
• 检测方形二维码的算法第一步先找出图像中的直线，再检测其是否能拼成四边形，因此确保二维码四角无遮挡非常重要。此外如果二维码粘贴在矩形底板上，矩形底板的外框也会被边缘检测算法检出，若距离二维码较近的话可能产生误检。可以考虑1）扩大底板大小，避免底板外框和二维码外框混淆，2）改变底板形状，如增加圆角？3）或者通过纹理破坏直线边缘？
• 针对不同定位需求选取不同类型的二维码，如对YuMi的关节进行定位，因为其关节处有圆形的塑料盖，可能可以考虑使用圆形的二维码。有点工作在无人机与其载荷间进行定位时使用不同尺寸（大小已知）的圆盘

AR Tag §

• https://github.com/harshkakashaniya/AR-tag-detection

• https://medium.com/lifeandtech/custom-ar-tag-detection-tracking-manipulation-d7543b8569ea

• https://ieeexplore.ieee.org/abstract/document/1467495

• https://www.scitepress.org/papers/2017/64789/64789.pdf

• 也使用ar_track_alvar进行检测？

  • http://www.yahboom.net/public/upload/upload-html/1637060179/ARTag.html

    Alvar is newer and more advanced than ARToolkit.

  http://blog.chinaunix.net/uid-27875-id-5823988.html

Alvar §

• 使用ROS的ar_track_alvar包跟踪AR Tag

• 参考教程？

  • https://marielleeusebio.me/personal/2021/02/16/AR_tags.html
  • https://github.com/atomoclast/ar_tag_toolbox
  • https://zhuanlan.zhihu.com/p/451668784
  • https://zhuanlan.zhihu.com/p/183830780
  • https://zhuanlan.zhihu.com/p/71602482

ArUco §

• 尺寸：4x4~7x7。尺寸是指像素尺寸（几乘几的格子），不包括外框
• 生成ArUco marker：链接
• OpenCV内置
  • make sure opencv-python is not installed
  • install opencv-contrib-python
  • ArUoc over AprilTag

    ArUco over AprilTag

    1. ArUco markers are built into the OpenCV library via the cv2.aruco submodule (i.e., we don’t need additional Python packages).
    2. The OpenCV library itself can generate ArUco markers via the cv2.aruco.drawMarker function.
    3. There are online ArUco generators that we can use if we don’t feel like coding (unlike AprilTags where no such generators are easily found).
    4. There are ROS (Robot Operating System) implementations of ArUco markers.
    5. And from an implementation perspective, ArUco marker detections tend to be more accurate, even when using the default parameters.

• aruco_ros

通过OpenCV定位ArUco §

• 分为初始化、检出、三维定位三个步骤，参考详情

QR code §

• 生成QR码
• QR.io

通过OpenCV定位QR code §

使用OpenCV定位QR码

AprilTag §

CALTag §