[wish] Auto-generate gitk's pretty pictures

Being an ignorant in matters Tk, I am wondering whether it'd be possible to hack gitk so that it renders the top canvas into a file. gitweb doesn't give people any hints of how the heads are related, so I am working on the idea of running an hourly cron on the server that does

 gitk -d --all --max-count=1000 --prettypic=foo.png

and link to the png from gitweb. Is it easier to trick gitk to do it, or should I be thinking of porting the logic to some other script? (Possibly in Perl using GD).

cheers,

martin