BF,ENH: ImageWrapper and naninfrange have support for structured

arrays (e.g. RGB data)

fsl/data/imagewrapper.py

@@ -303,9 +303,11 @@ class ImageWrapper(notifier.Notifier):
         # data range for each volume/slice/vector
         #
         # We use nan as a placeholder, so the
-        # dtype must be non-integral
+        # dtype must be non-integral. The
+        # len(dtype) check takes into account
+        # structured data (e.g. RGB)
         dtype = self.__image.get_data_dtype()
-        if np.issubdtype(dtype, np.integer):
+        if np.issubdtype(dtype, np.integer) or len(dtype) > 0:
             dtype = np.float32
         self.__volRanges = np.zeros((nvols, 2),
                                     dtype=dtype)

fsl/utils/naninfrange.py

@@ -23,6 +23,12 @@ def naninfrange(data):
     use an alternate approach to calculating the minimum/maximum.
     """
 
+    # For structured arrays, we assume that
+    # all fields are numeric, and we simply
+    # take the range across all fields
+    if len(data.dtype) > 0:
+        data = np.concatenate([data[n] for n in data.dtype.names])
+
     if not np.issubdtype(data.dtype, np.floating):
         return data.min(), data.max()