I agree with Werner, you are far better off running ghostscript,
netpbm or Image/Convert-Magick on the postscript output.
Too heavy weight and it forces me to bundle groff with my products.
Nothing against groff, I clearly love it, but I don't want that much
stuff in my install image.
I fear there isn't such a thing. At least I'm not aware of any
program which directly translates pic code without using groff. A
solution could be to add a third mode to pic: Handling text as HTML
directly; then the pic diagram could be used as a background image. I
don't know whether this approach works at all, and I don't have time
to play around.