In scipy module, there is a function named misc.lena which can return an array of numpy.ndarray type. If you use this array as parameter of matplotlib.pyplot.imshow and then call the matplotlib.pyplot.imshow function, an image will be shown. The shown image is generated by the numpy.ndarray array.
How to convert an arbitrary image into an array of numpy.ndarray type? -- http://mail.python.org/mailman/listinfo/python-list