Scripting from the command line

[darkling]

Is there any way that I can run a command-line script to (e.g.) export a .pxo file as some other format such as PNG or PPM?

For example, in inkscape, I can run it with various ``--export-*` options to select a region and output size/format and generate a result without going near the GUI. I've looked at the docs for scripting, but they're a bit cryptic, and don't really tell me how to do anything -- and I get the feeling they're for adding tooling accessible via the GUI, which isn't what I want.