gsrenderfont produces bitmaps for a PostScript font, using Ghostscript
(version 2.4).  Following is an outline (no pun intended) of the algorithm.

It first runs Ghostscript on `writefont.PS' on a PostScript
input font, call it `foo'.  This produces
  1) foo.pbm (the bitmaps)
  2) foo.xifi (an ifi without bounding box counts)
  3) foo.bfi (the character bitmap heights and character count)

Then it runs bbcount.  This reads
  1) foo.pbm and
  2) foo.bfi
and writes
  1) foo.bbs (bounding box counts for each character).

Then it runs awk on `fixifibb.awk'.  This reads
  1) foo.xifi
  2) foo.bbs
and writes
  1) foo.ifi (the image information for foo, including the bounding box counts)

Then it runs imagetofont (which has its own source directory).  This reads
  1) foo.pbm
  2) foo.ifi
and writes
  1) foo.NNNNgf
where the NNNN is the resolution.
