[Printing-user-general] Print to file?

I'd like to install a "printer" on my system which actually just
generates something like .jpg or .png images (one per page) in
a directory somewhere.

This seems like it ought to be simple, but with so many bits and
pieces fitting together in mysterious ways I'm not sure exactly
the best way to proceed (and am kind of surprised I haven't
found an example of someone already doing this).

Any suggestions as to the "right" approach?