ENH: Move PIL import to local scope.

Now it is optional unless someone wants PNG conversion in dicomfs. Note
this fact in the installation docs.

Author: mih

doc/source/installation.rst

@@ -74,6 +74,7 @@ Requirements
 *  NumPy_ 1.2 or greater
 *  SciPy_ (for full SPM-ANALYZE support)
 *  PyDICOM_ 0.9.5 or greater (for DICOM support)
+*  `Python Imaging Library`_ (for PNG conversion in DICOMFS)
 *  nose_ 0.11 or greater (to run the tests)
 *  sphinx_ (to build the documentation)
 

doc/source/links_names.txt

@@ -92,6 +92,7 @@
 .. _setuptools: http://pypi.python.org/pypi/setuptools
 .. _distribute: http://packages.python.org/distribute
 .. _datapkg: http://okfn.org/projects/datapkg
+.. _python imaging library: http://www.pythonware.com
 
 .. Python imaging projects
 .. _PyMVPA: http://www.pymvpa.org

nibabel/dft.py

@@ -15,7 +15,6 @@
 import numpy
 import nibabel
 import sqlite3
-import PIL.Image
 import dicom
 
 _study_instance_uid_tag  = dicom.tag.Tag(0x0020, 0x000d)
@@ -133,6 +132,7 @@ def __getattribute__(self, name):
         return val
 
     def as_png(self, index=None, scale_to_slice=True):
+        import PIL.Image
         if index is None:
             index = len(self.storage_instances) / 2
         d = self.storage_instances[index].dicom()