lp spooler and PostScript

[Steve Belle]

I have encountered a curious problem.  One of our guys here has, on
a Personal Iris, some image files in the SGI rgb format.  He wants
hardcopy of these images.  We have a Tek Phaser PX color printer.
I thought I had read that the lp spooler knew how to handle
the rgb formats.  When the image.rgb file is sent to the printer
through lp, the image comes out on paper, but it is not in color.
I converted the .rgb file to a color postscript file and sent
the image.ps file through lp.  This results in a strange header
page coming out of the printer.  It appears that the lp spooler 
corrupted the file so that the printer did not recognize it as
PostScript.  I tried cat-ing the file and redirecting to the 
printer device, and this worked; the color picture was printed.

I wasn't around when the Iris and the printer were bought
and set-up, so I don't know much about the configuration.
Is the type of behavior I described normal, or do I need to
dig into the details of how this workstation and printer
are configured?

Steve Belle
PRC
belle at skipper.dfrf.nasa.gov