Additional PostScript commands being given to Ghostscript by ImageMagick

Hi,

I see when converting a PDF to a raster asset (PNG in this case), the
Ghostscript command line contains two input files, a copy of the original
PDF and another file. I am curious as to how the contents of this file are
determined, or what they are exactly. If someone would be so kind as point
to me to the correct place in the source, I would be appreciative. Note:
I've looked in coders/pdf.c and coders/ps.c and while I'm guessing it is
determined there, I can't find the exact place.

-Ryan Kelly