You probably meant pdflatex foo.tex, no? That throws an error that it can't find standalone.cls, so I installed it with tlmgr install standalone, after which it complains about not knowing preview.sty, so I tlmgr install preview and voila. It works. Reading the documentation for latex-pict, I now realize that I should have checked that both of those are installed, but it was not crystal clear to me that those were requirements. Maybe make it even more obvious by saying "Ensure that you have the following three packages installed ... You can check that your setup works by running pdflatex ... ....
The new image looks much nicer:
Thanks a lot for this awesome package!