image_proc's TrackMarkerNode requires OpenCV 4.5.1 or greater

[tedsteiner]

The TrackMarkerNode includes the OpenCV header <opencv2/core/quaternion.hpp>. Currently the image_proc CMakeLists.txt file specifies that OpenCV 3.2.0 is the minimum required version. However, quaternion.hpp wasn't added to OpenCV until version 4.5.1. The result is a compiler error on earlier versions of OpenCV, such as those provided by Ubuntu 20.04 (4.2.0).

At first I thought this was maybe just a header left unintentionally because it's a bit subtle, but here's where the OpenCV quaternion header is used:

      // Convert angle-axis to quaternion
      cv::Quatd q = cv::Quatd::createFromRvec(rvecs[0]);
      pose.pose.orientation.x = q.x;
      pose.pose.orientation.y = q.y;
      pose.pose.orientation.z = q.z;
      pose.pose.orientation.w = q.w;
      pub_->publish(pose);

Is there maybe some other code that already exists somewhere to do this conversion without using the cv::Quatd class?

This causes a build error when trying to build ROS 2 Jazzy from source with the perception variant on Ubuntu 20.04 with the Apt-provided version of libopencv-dev. The original merge request was here: #930

[mikeferguson]

A couple thoughts:

• We should fix the opencv version requirement on the Jazzy/rolling branches to be correct - that is an oversight
• Jazzy targets 24.04, 20.04 is pretty old for us to also target.
• It looks like even 22.04 has opencv 4.5.4 - so that meets the minimum all the way back to Humble (which, didn't actually get this feature backported)

[mikeferguson]

Note: this is not to say we wouldn't merge a PR that addressed this so it would run on 20.04 - it's just not something the maintainers are likely to find time to tackle

[tedsteiner]

Thanks for the quick response! I appreciate that 20.04 is pretty old to still support.

Instead of using OpenCV for this conversion, how about using TF2, which is already a dependency of image_pipeline (both depth_image_proc and image_rotate)? It looks like this function would do the same thing: https://docs.ros.org/en/jazzy/p/tf2/generated/classtf2_1_1Quaternion.html#_CPPv4N3tf210Quaternion10QuaternionERK7Vector3RK9tf2Scalar.

If so, it should be a pretty simple change. But I don't use TrackMarkerNode and it doesn't appear to have unit tests so if I did make the change I wouldn't be able to verify that it has the same behavior.

[hacker1024]

On a similar note, OpenCV > 4.6.0 doesn't work with this node either, as the ArUco API changed.