RF: Restore and deprecate loadsave helpers

Author: effigies

nibabel/loadsave.py

@@ -10,6 +10,7 @@
 """ Utilities to load and save image objects """
 
 import numpy as np
+import warnings
 
 from .filename_parser import splitext_addext
 from .openers import ImageOpener
@@ -33,7 +34,6 @@ def load(filename, **kwargs):
     img : ``SpatialImage``
        Image of guessed type
     '''
-
     sniff = None
     for image_klass in all_image_classes:
         is_valid, sniff = image_klass.path_maybe_image(filename, sniff)
@@ -44,6 +44,31 @@ def load(filename, **kwargs):
                          filename)
 
 
+@np.deprecate
+def guessed_image_type(filename):
+    """ Guess image type from file `filename`
+
+    Parameters
+    ----------
+    filename : str
+        File name containing an image
+
+    Returns
+    -------
+    image_class : class
+        Class corresponding to guessed image type
+    """
+    warnings.warn('guessed_image_type is deprecated', DeprecationWarning)
+    sniff = None
+    for image_klass in all_image_classes:
+        is_valid, sniff = image_klass.path_maybe_image(filename, sniff)
+        if is_valid:
+            return image_klass
+
+    raise ImageFileError('Cannot work out file type of "%s"' %
+                         filename)
+
+
 def save(img, filename):
     ''' Save an image to file adapting format to `filename`
 
@@ -178,3 +203,46 @@ def read_img_data(img, prefer='scaled'):
         if prefer == 'scaled':
             return hdr.data_from_fileobj(fileobj)
         return hdr.raw_data_from_fileobj(fileobj)
+
+
+@np.deprecate
+def which_analyze_type(binaryblock):
+    """ Is `binaryblock` from NIfTI1, NIfTI2 or Analyze header?
+
+    Parameters
+    ----------
+    binaryblock : bytes
+        The `binaryblock` is 348 bytes that might be NIfTI1, NIfTI2, Analyze,
+        or None of the the above.
+
+    Returns
+    -------
+    hdr_type : str
+        * a nifti1 header (pair or single) -> return 'nifti1'
+        * a nifti2 header (pair or single) -> return 'nifti2'
+        * an Analyze header -> return 'analyze'
+        * None of the above -> return None
+
+    Notes
+    -----
+    Algorithm:
+
+    * read in the first 4 bytes from the file as 32-bit int ``sizeof_hdr``
+    * if ``sizeof_hdr`` is 540 or byteswapped 540 -> assume nifti2
+    * Check for 'ni1', 'n+1' magic -> assume nifti1
+    * if ``sizeof_hdr`` is 348 or byteswapped 348 assume Analyze
+    * Return None
+    """
+    warnings.warn('which_analyze_type is deprecated', DeprecationWarning)
+    from .nifti1 import header_dtype
+    hdr_struct = np.ndarray(shape=(), dtype=header_dtype, buffer=binaryblock)
+    bs_hdr_struct = hdr_struct.byteswap()
+    sizeof_hdr = hdr_struct['sizeof_hdr']
+    bs_sizeof_hdr = bs_hdr_struct['sizeof_hdr']
+    if 540 in (sizeof_hdr, bs_sizeof_hdr):
+        return 'nifti2'
+    if hdr_struct['magic'] in (b'ni1', b'n+1'):
+        return 'nifti1'
+    if 348 in (sizeof_hdr, bs_sizeof_hdr):
+        return 'analyze'
+    return None

nibabel/tests/test_image_load_save.py

@@ -260,3 +260,62 @@ def test_filename_save():
             del rt_img
         finally:
             shutil.rmtree(pth)
+
+
+def test_analyze_detection():
+    # Test detection of Analyze, Nifti1 and Nifti2
+    # Algorithm is as described in loadsave:which_analyze_type
+    def wat(hdr):
+        return nils.which_analyze_type(hdr.binaryblock)
+    n1_hdr = Nifti1Header(b'\0' * 348, check=False)
+    assert_equal(wat(n1_hdr), None)
+    n1_hdr['sizeof_hdr'] = 540
+    assert_equal(wat(n1_hdr), 'nifti2')
+    assert_equal(wat(n1_hdr.as_byteswapped()), 'nifti2')
+    n1_hdr['sizeof_hdr'] = 348
+    assert_equal(wat(n1_hdr), 'analyze')
+    assert_equal(wat(n1_hdr.as_byteswapped()), 'analyze')
+    n1_hdr['magic'] = b'n+1'
+    assert_equal(wat(n1_hdr), 'nifti1')
+    assert_equal(wat(n1_hdr.as_byteswapped()), 'nifti1')
+    n1_hdr['magic'] = b'ni1'
+    assert_equal(wat(n1_hdr), 'nifti1')
+    assert_equal(wat(n1_hdr.as_byteswapped()), 'nifti1')
+    # Doesn't matter what magic is if it's not a nifti1 magic
+    n1_hdr['magic'] = b'ni2'
+    assert_equal(wat(n1_hdr), 'analyze')
+    n1_hdr['sizeof_hdr'] = 0
+    n1_hdr['magic'] = b''
+    assert_equal(wat(n1_hdr), None)
+    n1_hdr['magic'] = 'n+1'
+    assert_equal(wat(n1_hdr), 'nifti1')
+    n1_hdr['magic'] = 'ni1'
+    assert_equal(wat(n1_hdr), 'nifti1')
+
+
+def test_guessed_image_type():
+    # Test whether we can guess the image type from example files
+    assert_equal(nils.guessed_image_type(
+        pjoin(DATA_PATH, 'example4d.nii.gz')),
+        Nifti1Image)
+    assert_equal(nils.guessed_image_type(
+        pjoin(DATA_PATH, 'nifti1.hdr')),
+        Nifti1Pair)
+    assert_equal(nils.guessed_image_type(
+        pjoin(DATA_PATH, 'example_nifti2.nii.gz')),
+        Nifti2Image)
+    assert_equal(nils.guessed_image_type(
+        pjoin(DATA_PATH, 'nifti2.hdr')),
+        Nifti2Pair)
+    assert_equal(nils.guessed_image_type(
+        pjoin(DATA_PATH, 'tiny.mnc')),
+        Minc1Image)
+    assert_equal(nils.guessed_image_type(
+        pjoin(DATA_PATH, 'small.mnc')),
+        Minc2Image)
+    assert_equal(nils.guessed_image_type(
+        pjoin(DATA_PATH, 'test.mgz')),
+        MGHImage)
+    assert_equal(nils.guessed_image_type(
+        pjoin(DATA_PATH, 'analyze.hdr')),
+        Spm2AnalyzeImage)