fix fftn_centered_t and ifftn_centered_t

Signed-off-by: Puyang Wang <[email protected]>

Author: XwK-P

monai/networks/blocks/fft_utils_t.py

@@ -139,21 +139,17 @@ def ifftn_centered_t(ksp: Tensor, spatial_dims: int, is_complex: bool = True) ->
             output2 = ifftn_centered(ksp, spatial_dims=2, is_complex=True)
     """
     # define spatial dims to perform ifftshift, fftshift, and ifft
-    shift = list(range(-spatial_dims, 0))
+    dims = list(range(-spatial_dims, 0))
     if is_complex:
         if ksp.shape[-1] != 2:
             raise ValueError(f"ksp.shape[-1] is not 2 ({ksp.shape[-1]}).")
-        shift = list(range(-spatial_dims - 1, -1))
-    dims = list(range(-spatial_dims, 0))
+        x = torch.view_as_complex(ksp)
 
-    x = ifftshift(ksp, shift)
+    x = ifftshift(ksp, dims)
 
-    if is_complex:
-        x = torch.view_as_real(torch.fft.ifftn(torch.view_as_complex(x), dim=dims, norm="ortho"))
-    else:
-        x = torch.view_as_real(torch.fft.ifftn(x, dim=dims, norm="ortho"))
+    x = fftshift(torch.fft.ifftn(x, dim=dims, norm="ortho"), dims)
 
-    out: Tensor = fftshift(x, shift)
+    out: Tensor = torch.view_as_real(x)
 
     return out
 
@@ -191,12 +187,12 @@ def fftn_centered_t(im: Tensor, spatial_dims: int, is_complex: bool = True) -> T
     if is_complex:
         if im.shape[-1] != 2:
             raise ValueError(f"img.shape[-1] is not 2 ({im.shape[-1]}).")
-        x = torch.view_as_complex(ifftshift(im, [d - 1 for d in dims]))
-    else:
-        x = ifftshift(im, dims)
+        x = torch.view_as_complex(im)
+
+    x = ifftshift(im, dims)
 
-    x = torch.view_as_real(torch.fft.fftn(x, dim=dims, norm="ortho"))
+    x = fftshift(torch.fft.fftn(x, dim=dims, norm="ortho"), dims)
 
-    out: Tensor = fftshift(x, [d - 1 for d in dims])
+    out: Tensor = torch.view_as_real(x)
 
     return out