Function requires_interp

monai/transforms/lazy/utils.py:122–152

Check whether the transformation matrix suggests voxel-wise interpolation. Returns None if the affine matrix suggests interpolation. Otherwise, the matrix suggests that the resampling could be achieved by simple array operations such as flip/permute/pad_nd/slice; in this case this

(matrix, atol=AFFINE_TOL)

def requires_interp(matrix, atol=AFFINE_TOL):
    """
    Check whether the transformation matrix suggests voxel-wise interpolation.

    Returns None if the affine matrix suggests interpolation.
    Otherwise, the matrix suggests that the resampling could be achieved by simple array operations
    such as flip/permute/pad_nd/slice; in this case this function returns axes information about simple axes
    operations.

    Args:
        matrix: the affine matrix to check.
        atol: absolute tolerance for checking if the matrix is close to an integer.
    """
    matrix = convert_to_numpy(matrix, wrap_sequence=True)
    s = matrix[:, -1]
    if not np.allclose(s, np.round(s), atol=atol):
        return None

    ndim = len(matrix) - 1
    ox, oy = [], [0]
    for x, r in enumerate(matrix[:ndim, :ndim]):
        for y, c in enumerate(r):
            if np.isclose(c, -1, atol=atol) or np.isclose(c, 1, atol=atol):
                y_channel = y + 1  # the returned axis index starting with channel dim
                if x in ox or y_channel in oy:
                    return None
                ox.append(x)
                oy.append(y_channel)
            elif not np.isclose(c, 0.0, atol=atol):
                return None
    return oy


__override_lazy_keywords = {*list(LazyAttr), "atol"}