fix decimal rescale values causing Decimal data frame

nibabel/nicom/dicomwrappers.py

@@ -353,8 +353,9 @@ def is_same_series(self, other):
         return True
 
     def _scale_data(self, data):
-        scale = self.get('RescaleSlope', 1)
-        offset = self.get('RescaleIntercept', 0)
+        # depending on pydicom and dicom files, values might need casting from Decimal to float
+        scale = float(self.get('RescaleSlope', 1))
+        offset = float(self.get('RescaleIntercept', 0))
         # a little optimization.  If we are applying either the scale or
         # the offset, we need to allow upcasting to float.
         if scale != 1:

nibabel/nicom/tests/test_dicomwrappers.py

@@ -31,6 +31,7 @@
     DATA = None
 DATA_FILE_B0 = pjoin(IO_DATA_PATH, 'siemens_dwi_0.dcm.gz')
 DATA_FILE_SLC_NORM = pjoin(IO_DATA_PATH, 'csa_slice_norm.dcm')
+DATA_FILE_DEC_RSCL = pjoin(IO_DATA_PATH, 'decimal_rescale.dcm')
 
 # This affine from our converted image was shown to match our image
 # spatially with an image from SPM DICOM conversion. We checked the
@@ -171,3 +172,10 @@ def test_assert_parallel():
     dw = didw.wrapper_from_file(DATA_FILE_SLC_NORM)
     dw.image_orient_patient = np.c_[[1., 0., 0.], [0., 1., 0.]]
     assert_raises(AssertionError, dw.__getattribute__, 'slice_normal')
+
+@dicom_test
+def test_decimal_rescale():
+    #Test that we don't get back a data array with dtpye np.object when our 
+    #rescale slope is a decimal
+    dw = didw.wrapper_from_file(DATA_FILE_DEC_RSCL)
+    assert dw.get_data().dtype != np.object