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Introduction
------------

pywcs is a set of routines for handling the FITS World Coordinate
System (WCS) standard.  It is a thin wrapper around the high- and
mid-level interfaces of Dr. Mark Calabretta's WCSLIB available here:

  http://www.atnf.csiro.au/people/mcalabre/WCS/

In addition, there are extensions (written in C) to support Spitzer
Simple Imaging Polynomial (SIP) convention keywords and Paper IV table
lookup distortion.

pywcs is alpha-quality software.  Please direct any questions to:

  Michael Droettboom
  mdroe@stsci.edu

The current version is focused on providing basic access to the
functionality in WCSLIB.  Future releases will have better integration
with PyFITS and more Python-specific utilities.

Build instructions
------------------

pywcs includes its own copy of WCSLIB.

pywcs requires:

  - Numpy 1.3 or later
  - pyfits 1.4 or later

pywcs uses the standard Python distutils system to build and install
itself.  From the command line run::

    python setup.py install

to install pywcs.

Building documentation
----------------------

Optionally, the API documentation can be built using epydoc
(http://epydoc.sourceforge.net).  Version 3.0beta1 or later of epydoc
must be used.  Earlier versions will not document all of the members.

After installing pywcs, type::

    epydoc --inheritance=included --no-private pywcs

The API documentation is also available online at:

    http://stsdas.stsci.edu/astrolib/pywcs/index.html

General usage instructions
--------------------------

TODO: The information below is out-of-date.

The basic workflow is as follows:

    1. ``import pywcs``

    2. Call ``pywcs.parse_image_header()`` with a raw FITS header or
    ``pywcs.parse_hdulist()`` with a PyFITS hdulist.  This will return
    a list containing all of the WCS transformations specified in the
    FITS file.

    3. Optionally, if the FITS file uses any deprecated or
    non-standard features, you may need to call one of the ``fix``
    methods on the object.

    4. Select the correct ``Wcs`` transform object from the list, and
    convert coordinates using the ``.p2s()`` or ``.s2p()`` methods.

See the API documentation for usage details about these methods.
There are also examples in the examples/ directory.