Python modules for image / map manipulation?

[Stewart Midwinter]

I would like to do some image / map manipulation with Python.

I've got a very large map file in .png format. My thought is to chop
it up into small tiles using some method. What Python module would be
helpful for this?

Next, when I obtain the start and end co-ordinates of a user's trip,
I'd like to stitch together the approriate tiles and present the
images that show the terrain the user has travelled over.

Lastly, I'd like to plot the GPS tracklog of the trip on top of the map.

Any suggestions for modules or projects to help accomplish this? It's
a non-commercial hobby application.

thanks,