Python wrappers for gdcm

Working with Python

• cd GDCM_HOME
• export PYTHONPATH=`pwd`
• cd gdcmPython
• ln -s .libs/pygdcm.so _gdcm.so
  (this is because automake doesn't allow the building of libraries whose name starts with an underscore. Since we need the wrapper library to be named _gdcm [because swig automaticatily uses this name when building the shadow classes], automake generates pygdcm.so and at install stage stage renames it to _gdcm.so).
• You can then use gdcmPython for manual test/demos
  1. cd GDCM_HOME/gdcmPython/demo
  2. python PrintHeader.py

  Depending on the cmake flags you used in order to compile gdcm could
  be wrapped in two ways:
  - the first python wrappers of gdcm uses Swig (http://www.swig.org). These
    are the one generated when using autogen.sh --enable-python.
    The entry point here is the file gdcmPython/gdcm.i which uses the
    Swig syntax. As the last lines of this file (the ones starting
    with the %include directive) only some classes are wrapped for python.
    In theory only the library interface (basically the classes gdcmHeader
    and gdcmFile) should be wrapped, but the time being some additional
    classes are added (just to make sure those classes are Swig compatible:
    swig is here used as some link checker!?).
    Since gdcm is written in C++, Swig will produce two different outputs:
      -- some C based low level wrapper (see gdcmPython/gdcm_wrap.c)
      -- some Python based object oriented so called "shadow classes" (see
         file gdcmPython/gdcm.py)
    We also added the file gdcmPython/__init__.py which is the one that
    actually gets loaded when one uses the gdcmPython Python package.
    The file __init__.py loads the Swig generated shadow classes (gdcm.py)
    but will only re-export the interface of gdcm which corresponds to
    the lines :
       gdcmHeader = gdcm.gdcmHeader
       gdcmDictSet = gdcm.gdcmDictSet
       gdcmFile = gdcm.gdcmFile
       [etc.]
    Hence this whole Swig wrapping process is quite odd since we shall
    wrap more classes (%include in swig.i) that eventually get exported to
    the final user by gdcmPython/__init__.py.
  - the second python wrappers uses the vtk (http://public.kitware.com/VTK/)
    native wrappers i.e. the binary vtkWrapPython. But it should be noticed
    that the purpose is here a bit different than the one of the Swig
    generated Python wrappers. When using vtkWrapPython the goal is to
    wrap a single vtk class namely vtkGdcmReader as defined in files
    vtk/vtkGdcmReader.h and vtk/vtkGdcmReader.cxx (and of course those
    files are hand made vtk oriented wrappers of gdcm).
    Those wrappers are the one generated when using
       autogen.sh --enable-python --enable-vtk
  - In order to understand the difference between both wrappers you should
    compare both demo scripts gdcmPython/demo/vtkGdcmDemo.py and
    gdcmPython/demo/vtkGdcmReader.py. The first one only uses the
    Swig wrapped classes ("from gdcmPython import gdcmHeader') as opposed
    to vtkGdcmReader.py which also uses vtkWrapPython wrapped classes
    ("from gdcmPython.vtkgdcmPython import *").