Merge pull request #259 from femaleprog/fix/b0map-shape-handling

Fix: Automatically upsample b0_map in MRIFourierCorrected if shapes m…

Author: femaleprog

src/mrinufft/operators/off_resonance.py

@@ -13,6 +13,8 @@
 from .base import FourierOperatorBase
 
 from .interfaces.utils import is_cuda_array
+import warnings
+from scipy.ndimage import zoom
 
 if CUPY_AVAILABLE:
     import cupy as cp
@@ -238,7 +240,18 @@ def __init__(
         self.shape = fourier_op.shape
         self.smaps = fourier_op.smaps
         self.autograd_available = fourier_op.autograd_available
-
+        if b0_map is not None:
+            b0_map = np.asarray(b0_map, dtype=np.float32)
+            if b0_map.shape != self.shape:
+                warnings.warn(
+                    f"B0 map shape {b0_map.shape} does not match operator \
+                    shape {self.shape}. "
+                    "Upsampling will be performed automatically.\
+                        Please ensure orientation is correct.",
+                    UserWarning,
+                )
+                zoom_factors = tuple(t / c for t, c in zip(self.shape, b0_map.shape))
+                b0_map = zoom(b0_map, zoom_factors, order=1)
         if B is not None and tl is not None:
             self.B = self.xp.asarray(B)
             self.tl = self.xp.asarray(tl)