cv.fillPoly() exception when running rtstruct.get_roi_mask_by_name

Hi there,

For my project, I've got multiple patients and I've generated an individual RTStructBuilder object per patient. Within the RTStructBuilder objects I have multiple ROIs (>50).

I am trying to use the rtstruct.get_roi_mask_by_name function to generate binary masks of each region, however I am getting an exception within image_helper.py line 278.

The exception occurs with some – but not all – of the ROIs within the RTStructBuilder object.

For instance, it will work with region1, e.g.:

mask = rtstruct.get_roi_mask_by_name('region1')

whereas say region2 will fail with the following error message:

Traceback (most recent call last):
  File "/Applications/PyCharm.app/Contents/plugins/python/helpers/pydev/pydevd.py", line 1483, in _exec
    pydev_imports.execfile(file, globals, locals)  # execute the script
  File "/Applications/PyCharm.app/Contents/plugins/python/helpers/pydev/_pydev_imps/_pydev_execfile.py", line 18, in execfile
    exec(compile(contents+"\n", file, 'exec'), glob, loc)
  File "/Users/tr17/Library/Application Support/JetBrains/PyCharm2021.2/scratches/load_rt.py", line 123, in <module>
    mask = rtstruct_TS.get_roi_mask_by_name('lung_upper_lobe_right')
  File "/Users/tr17/venv/prague/lib/python3.9/site-packages/rt_utils/rtstruct.py", line 113, in get_roi_mask_by_name
    return image_helper.create_series_mask_from_contour_sequence(
  File "/Users/tr17/venv/prague/lib/python3.9/site-packages/rt_utils/image_helper.py", line 247, in create_series_mask_from_contour_sequence
    mask[:, :, i] = get_slice_mask_from_slice_contour_data(
  File "/Users/tr17/venv/prague/lib/python3.9/site-packages/rt_utils/image_helper.py", line 281, in get_slice_mask_from_slice_contour_data
    cv.fillPoly(img=slice_mask, pts = polygons, color = 1)
cv2.error: OpenCV(4.7.0) /Users/xperience/GHA-OCV-Python/_work/opencv-python/opencv-python/opencv/modules/imgproc/src/drawing.cpp:2402: error: (-215:Assertion failed) p.checkVector(2, CV_32S) >= 0 in function 'fillPoly'

I've looked up the fillPoly error online and there are various posts about casting as int32, but I think you are already doing that properly.

I'm a bit stuck... much appreciated if you can help. Thanks in advance.