Relegate slicing to is_header, remove _minctest

Author: effigies

nibabel/minc1.py

@@ -272,7 +272,7 @@ class MincHeader(Header):
     # We don't use the data layout - this just in case we do later
     data_layout = 'C'
 
-    # 
+    # Number of bytes needed to distinguish Minc1 and Minc2 headers
     sniff_size = 4
 
     def data_to_fileobj(self, data, fileobj, rescale=True):
@@ -287,7 +287,7 @@ def data_from_fileobj(self, fileobj):
 class Minc1Header(MincHeader):
     @classmethod
     def is_header(klass, binaryblock):
-        return binaryblock != b'\211HDF'
+        return binaryblock[:4] != b'\211HDF'
 
 
 class Minc1Image(SpatialImage):

nibabel/minc2.py

@@ -137,7 +137,7 @@ def get_scaled_data(self, sliceobj=()):
 class Minc2Header(MincHeader):
     @classmethod
     def is_header(klass, binaryblock):
-        return binaryblock == b'\211HDF'
+        return binaryblock[:4] == b'\211HDF'
 
 
 class Minc2Image(Minc1Image):
@@ -167,9 +167,5 @@ def from_file_map(klass, file_map):
         data = klass.ImageArrayProxy(minc_file)
         return klass(data, affine, header, extra=None, file_map=file_map)
 
-    @classmethod
-    def _minctest(klass, binaryblock):
-        return binaryblock[:4] == b'\211HDF'
-
 
 load = Minc2Image.load

nibabel/spatialimages.py

@@ -909,7 +909,7 @@ def is_image(klass, filename, sniff=None):
                 sniff_size = np.max([1024, klass.header_class.sniff_size])
                 with BinOpener(metadata_filename, 'rb') as fobj:
                     sniff = fobj.read(sniff_size)
-            return klass.header_class.is_header(sniff[:klass.header_class.sniff_size]), sniff
+            return klass.header_class.is_header(sniff), sniff
         except Exception as e:
             # Can happen if: file doesn't exist,
             #   filesize < necessary sniff size (this happens!)