BF+TST: Fix 'frame_order' for single frame files

nibabel/nicom/dicomwrappers.py

@@ -532,8 +532,8 @@
 class FrameFilter:
     """Base class for defining how to filter out (ignore) frames from a multiframe file
 
-    It is guaranteed that the `applies` method will on a dataset before the `keep` method
-    is called on any of the frames inside.
+    It is guaranteed that the `applies` method will called on a dataset before the `keep`
+    method is called on any of the frames inside.
     """
 
     def applies(self, dcm_wrp) -> bool:
@@ -549,7 +549,7 @@
     """Filter out all but one `StackID`"""
 
     def __init__(self, keep_id=None):
-        self._keep_id = keep_id
+        self._keep_id = str(keep_id) if keep_id is not None else None
 
     def applies(self, dcm_wrp) -> bool:
         first_fcs = dcm_wrp.frames[0].get('FrameContentSequence', (None,))[0]
@@ -562,10 +562,16 @@
             self._selected = self._keep_id
         if len(stack_ids) > 1:
             if self._keep_id is None:
+                try:
+                    sids = [int(x) for x in stack_ids]
+                except:
+                    self._selected = dcm_wrp.frames[0].FrameContentSequence[0].StackID
+                else:
+                    self._selected = str(min(sids))
                 warnings.warn(
-                    'A multi-stack file was passed without an explicit filter, just using lowest StackID'
+                    'A multi-stack file was passed without an explicit filter, '
+                    f'using StackID = {self._selected}'
                 )
-                self._selected = min(stack_ids)
             return True
         return False
 
@@ -707,6 +713,7 @@
 
     @cached_property
     def frame_order(self):
+        """The ordering of frames to make nD array"""
         if self._frame_indices is None:
             _ = self.image_shape
         return np.lexsort(self._frame_indices.T)
@@ -742,14 +749,20 @@
         rows, cols = self.get('Rows'), self.get('Columns')
         if None in (rows, cols):
             raise WrapperError('Rows and/or Columns are empty.')
-        # Check number of frames, initialize array of frame indices
+        # Check number of frames and handle single frame files
         n_frames = len(self.frames)
+        if n_frames == 1:
+            self._frame_indices = np.array([[0]], dtype=np.int64)
+            return (rows, cols)
+        # Initialize array of frame indices
         try:
             frame_indices = np.array(
                 [frame.FrameContentSequence[0].DimensionIndexValues for frame in self.frames]
             )
         except AttributeError:
             raise WrapperError("Can't find frame 'DimensionIndexValues'")
+        if len(frame_indices.shape) == 1:
+            frame_indices = frame_indices.reshape(frame_indices.shape + (1,))
         # Determine the shape and which indices to use
         shape = [rows, cols]
         curr_parts = n_frames

nibabel/nicom/tests/test_dicomwrappers.py

@@ -427,13 +427,6 @@
         generate ipp values so slice location is negatively correlated with slice index
     """
 
-    class PrintBase:
-        def __repr__(self):
-            attr_strs = [
-                f'{attr}={getattr(self, attr)}' for attr in dir(self) if attr[0].isupper()
-            ]
-            return f"{self.__class__.__name__}({', '.join(attr_strs)})"
-
     class DimIdxSeqElem(pydicom.Dataset):
         def __init__(self, dip=(0, 0), fgp=None):
             super().__init__()
@@ -444,8 +437,8 @@
     class FrmContSeqElem(pydicom.Dataset):
         def __init__(self, div, sid):
             super().__init__()
-            self.DimensionIndexValues = div
-            self.StackID = sid
+            self.DimensionIndexValues = list(div)
+            self.StackID = str(sid)
 
     class PlnPosSeqElem(pydicom.Dataset):
         def __init__(self, ipp):
@@ -545,17 +538,28 @@
         with pytest.raises(didw.WrapperError):
             dw.image_shape
         fake_mf.Rows = 32
-        # No frame data raises WrapperError
+        # Single frame doesn't need dimension index values
+        assert dw.image_shape == (32, 64)
+        assert len(dw.frame_order) == 1
+        assert dw.frame_order[0] == 0
+        # Multiple frames do require dimension index values
+        fake_mf.PerFrameFunctionalGroupsSequence = [pydicom.Dataset(), pydicom.Dataset()]
         with pytest.raises(didw.WrapperError):
-            dw.image_shape
+            MFW(fake_mf).image_shape
         # check 2D shape with StackID index is 0
         div_seq = ((1, 1),)
         fake_mf.update(fake_shape_dependents(div_seq, sid_dim=0))
-        assert MFW(fake_mf).image_shape == (32, 64)
+        dw = MFW(fake_mf)
+        assert dw.image_shape == (32, 64)
+        assert len(dw.frame_order) == 1
+        assert dw.frame_order[0] == 0
         # Check 2D shape with extraneous extra indices
         div_seq = ((1, 1, 2),)
         fake_mf.update(fake_shape_dependents(div_seq, sid_dim=0))
-        assert MFW(fake_mf).image_shape == (32, 64)
+        dw = MFW(fake_mf)
+        assert dw.image_shape == (32, 64)
+        assert len(dw.frame_order) == 1
+        assert dw.frame_order[0] == 0
         # Check 2D plus time
         div_seq = ((1, 1, 1), (1, 1, 2), (1, 1, 3))
         fake_mf.update(fake_shape_dependents(div_seq, sid_dim=0))
@@ -569,7 +573,7 @@
         fake_mf.update(fake_shape_dependents(div_seq, sid_dim=0))
         with pytest.warns(
             UserWarning,
-            match='A multi-stack file was passed without an explicit filter, just using lowest StackID',
+            match='A multi-stack file was passed without an explicit filter,',
         ):
             assert MFW(fake_mf).image_shape == (32, 64, 3)
         # No warning if we expclitly select that StackID to keep
@@ -581,7 +585,7 @@
         fake_mf.update(fake_shape_dependents(div_seq, sid_seq=sid_seq))
         with pytest.warns(
             UserWarning,
-            match='A multi-stack file was passed without an explicit filter, just using lowest StackID',
+            match='A multi-stack file was passed without an explicit filter,',
         ):
             assert MFW(fake_mf).image_shape == (32, 64, 3)
         # No warning if we expclitly select that StackID to keep
@@ -590,6 +594,17 @@
         # Check for error when explicitly requested StackID is missing
         with pytest.raises(didw.WrapperError):
             MFW(fake_mf, frame_filters=(didw.FilterMultiStack(3),))
+        # StackID can be a string
+        div_seq = ((1,), (2,), (3,), (4,))
+        sid_seq = ('a', 'a', 'a', 'b')
+        fake_mf.update(fake_shape_dependents(div_seq, sid_seq=sid_seq))
+        with pytest.warns(
+            UserWarning,
+            match='A multi-stack file was passed without an explicit filter,',
+        ):
+            assert MFW(fake_mf).image_shape == (32, 64, 3)
+        assert MFW(fake_mf, frame_filters=(didw.FilterMultiStack('a'),)).image_shape == (32, 64, 3)
+        assert MFW(fake_mf, frame_filters=(didw.FilterMultiStack('b'),)).image_shape == (32, 64)
         # Make some fake frame data for 4D when StackID index is 0
         div_seq = ((1, 1, 1), (1, 2, 1), (1, 1, 2), (1, 2, 2), (1, 1, 3), (1, 2, 3))
         fake_mf.update(fake_shape_dependents(div_seq, sid_dim=0))
@@ -599,7 +614,7 @@
         fake_mf.update(fake_shape_dependents(div_seq, sid_dim=0))
         with pytest.warns(
             UserWarning,
-            match='A multi-stack file was passed without an explicit filter, just using lowest StackID',
+            match='A multi-stack file was passed without an explicit filter,',
         ):
             with pytest.raises(didw.WrapperError):
                 MFW(fake_mf).image_shape
@@ -638,7 +653,7 @@
         fake_mf.update(fake_shape_dependents(div_seq, sid_seq=sid_seq))
         with pytest.warns(
             UserWarning,
-            match='A multi-stack file was passed without an explicit filter, just using lowest StackID',
+            match='A multi-stack file was passed without an explicit filter,',
         ):
             with pytest.raises(didw.WrapperError):
                 MFW(fake_mf).image_shape
@@ -651,7 +666,7 @@
         fake_mf.update(fake_shape_dependents(div_seq, sid_dim=1))
         with pytest.warns(
             UserWarning,
-            match='A multi-stack file was passed without an explicit filter, just using lowest StackID',
+            match='A multi-stack file was passed without an explicit filter,',
         ):
             assert MFW(fake_mf).image_shape == (32, 64, 3)
         # Make some fake frame data for 4D when StackID index is 1