Invertd error when using spline interpolation order 0-5 (integers) in spacing transform

[chaoscls]

When I use spline interpolation order 0-5 (integers) for spacing transform, an error occurs if I invert item. I found may be there is a bug in https://github.com/Project-MONAI/MONAI/blob/a7bdb9d2611b611a9dd1a3183b025d1d8aeeea90/monai/transforms/utils.py#L1401C45-L1401C45. This line does not support current_mode is an integer.

Here is the error code:

import os.path as osp
import glob

from monai.transforms import LoadImaged, Spacingd, SaveImaged, Compose, Invertd
from tqdm import tqdm

tar_spacing = [1.5, 1.5, 1.5]

def main():
    data_dir = 'data'
    out_dir = 'out'
    image_files = sorted(glob.glob(osp.join(data_dir, 'images', '*.nii.gz')))
    label_files = sorted(glob.glob(osp.join(data_dir, 'labels', '*.nii.gz')))
    files_dict = [{'image': image, 'label': label} for image, label in zip(image_files, label_files)]
    
    transforms = Compose([
        LoadImaged(keys=['image', 'label'], image_only=True, ensure_channel_first=True),
        Spacingd(keys=['image', 'label'], pixdim=tar_spacing, mode=(1, 0), padding_mode='nearest'),
    ])

    post_transforms = Compose([
        Invertd(keys='label', transform=transforms, orig_keys='image', nearest_interp=True),
        SaveImaged(keys='label', output_dir=out_dir, output_postfix='', resample=False, separate_folder=False),
    ])

    for file_dict in tqdm(files_dict):
        data = transforms(file_dict)
        post_transforms(data)
    

if __name__ == '__main__':
    main()

And the error info:

Traceback (most recent call last):
  File "/opt/homebrew/Caskroom/miniforge/base/envs/dpl/lib/python3.10/site-packages/monai/transforms/transform.py", line 141, in apply_transform
    return _apply_transform(transform, data, unpack_items, lazy, overrides, log_stats)
  File "/opt/homebrew/Caskroom/miniforge/base/envs/dpl/lib/python3.10/site-packages/monai/transforms/transform.py", line 98, in _apply_transform
    return transform(data, lazy=lazy) if isinstance(transform, LazyTrait) else transform(data)
  File "/opt/homebrew/Caskroom/miniforge/base/envs/dpl/lib/python3.10/site-packages/monai/transforms/post/dictionary.py", line 683, in __call__
    transform_info = convert_applied_interp_mode(
  File "/opt/homebrew/Caskroom/miniforge/base/envs/dpl/lib/python3.10/site-packages/monai/transforms/utils.py", line 1395, in convert_applied_interp_mode
    return [convert_applied_interp_mode(x, mode=mode, align_corners=align_corners) for x in trans_info]
  File "/opt/homebrew/Caskroom/miniforge/base/envs/dpl/lib/python3.10/site-packages/monai/transforms/utils.py", line 1395, in <listcomp>
    return [convert_applied_interp_mode(x, mode=mode, align_corners=align_corners) for x in trans_info]
  File "/opt/homebrew/Caskroom/miniforge/base/envs/dpl/lib/python3.10/site-packages/monai/transforms/utils.py", line 1412, in convert_applied_interp_mode
    return {
  File "/opt/homebrew/Caskroom/miniforge/base/envs/dpl/lib/python3.10/site-packages/monai/transforms/utils.py", line 1413, in <dictcomp>
    k: convert_applied_interp_mode(trans_info[k], mode=mode, align_corners=align_corners) for k in trans_info
  File "/opt/homebrew/Caskroom/miniforge/base/envs/dpl/lib/python3.10/site-packages/monai/transforms/utils.py", line 1401, in convert_applied_interp_mode
    if current_mode[0] in _interp_modes:
TypeError: 'int' object is not subscriptable

[KumoLiu]

Hi @chaoscls, thanks for reporting, just create a PR to fix it.