Convert pickled RegularGridInterpolator objects to numpy saved files

src/whirlwind/_cost.py

@@ -1,8 +1,9 @@
 import importlib.resources
-import pickle
+from pathlib import Path
 
 import numpy as np
 import scipy.ndimage
+from scipy.interpolate import RegularGridInterpolator
 
 __all__ = [
     "calc_smooth_phase_gradients",
@@ -29,14 +30,24 @@ def calc_smooth_phase_gradients(igram):
     return phase_dy_smooth, phase_dx_smooth
 
 
+def _load_rgi(path: Path | str) -> RegularGridInterpolator:
+    """Reconstruct RegularGridInterpolator from saved data."""
+    data = np.load(path, allow_pickle=True)
+    return RegularGridInterpolator(
+        points=tuple(data['grid']),
+        values=data['values'],
+        method=str(data['method']),
+        bounds_error=bool(data['bounds_error']),
+        fill_value=float(data['fill_value']) if data['fill_value'] is not None else None,
+    )
+
+
 def load_carballo_pdf_splines():
     """ """
     files = importlib.resources.files(__package__)
 
-    with files.joinpath("carballo-pdf-0-spline.pkl").open("rb") as f:
-        spline_pdf0 = pickle.load(f)
-    with files.joinpath("carballo-pdf-1-spline.pkl").open("rb") as f:
-        spline_pdf1 = pickle.load(f)
+    spline_pdf0 = _load_rgi(files.joinpath("carballo-pdf-0-spline.npz"))
+    spline_pdf1 = _load_rgi(files.joinpath("carballo-pdf-1-spline.npz"))
 
     return spline_pdf0, spline_pdf1