Dumoping colour xterms to a greyscale postscript printer

[J H Mintz]

I am trying to dump an RS6000/320 GRASS Display Window to a postscript
rpinter.
I use the command:

xwd -bitmap | xpr -device ps | lpr -P<printername>

and this prints the xterm border with a blank interior.
Presumably, I need some way of converting the colour xwd dump
to greyscale.

Any ideas much appreciated.

Joe Mintz, Dept Computer Science, Birkbeck College