The PythonImagingLibrary (PIL) adds image processing capabilities to your Python interpreter. This library supports most popular file formats, and provides powerful image processing and graphics capabilities.
PIL comes with interfaces for TkInter and PythonWin. Many other GuiProgramming toolkits also support PIL images.
More here: http://www.pythonware.com/products/pil/index.htm
It seems no more maintained, but there's active fork instead: http://pypi.python.org/pypi/Pillow