[1.7.x] Replaced an instance of PIL with Pillow in the docs.

    Name of a model field which will be auto-populated with the width of the

    image each time the model instance is saved.

Requires the `Python Imaging Library`_.

Requires the `Pillow`_ library.

.. _Python Imaging Library: http://www.pythonware.com/products/pil/

.. _Pillow: http://python-imaging.github.io/Pillow/

By default, :class:`ImageField` instances are created as ``varchar(100)``

columns in your database. As with other fields, you can change the maximum