Camera calibration with april tags crashes

[fnobis]

The calibration works for a chessboard pattern. For the april tag is failed.

For the april tag, I printed the example from the repo: https://github.com/tier4/CalibrationTools/blob/tier4/universe/docs/resource/apriltag_grid_3x4.pdf to an A4 (210x297mm) piece of paper

I set the apriltag parameters to

rows = 4
cols  = 3
tag_size = 0.048
tag_spacing=0.25
min_index=0

as soon as the first apriltag marker is visible in the image the video stream freezes in the gui. The following error is printed in the command line when that happens:

[camera_calibrator-1] Traceback (most recent call last):
[camera_calibrator-1]   File "/workspace/build/intrinsic_camera_calibrator/intrinsic_camera_calibrator/camera_calibrator.py", line 1072, in process_detection_results
[camera_calibrator-1]     err_rms_rows, err_rms_cols, pct_err_rows, pct_err_cols = (
[camera_calibrator-1] TypeError: cannot unpack non-iterable numpy.float64 object

I also played around with different settings, e.g. less rows/columns but the programm crashed for all tested settings.

• Do you see the same behavior, or do some other settings need to be adapted?
• Is the script to create the april tag markers also somewhere available in the repo? I wanted to also use a higher resolution one.

[knzo25]

Thank you for the report.
We do not really recommend using the apriltags, at least not fir highly distorted images.
During some newly developed features, we broke things as apriltag boards do not necessarily constitute regular grids.

I will send either a PR that brings apriltag to conformity to the rest of the code base, or fix the code so that we can take advantage of apriltag boards better

🙏