altering postscript code on the fly to get pure black and white

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altering postscript code on the fly to get pure black and white
Hello, is it possible to alter postscript code (not manually, but on
the fly via a script or utility or whatever) before it is sent to a
printer? I'm guessing not, but just thought i'd ask just in case. I
want to convert the postscript code so that it prints pure black and
white, no greyscale. Our users are complaining that the greyscale is
coming out too dim. I was thinking about inserting the following line
at the beginning of the postscript stream,

{.999 lt {0}{1}ifelse} settransfer

Alternatively, I have considered setting up the printer queue so that
it prints to a postscript file instead of sending it to the printer
(This is done by setting the local port to a file path instead of an
IP address). Then altering the file via some script, then sending it
to the printer. Although, this really doesn't work well in a
multiuser environment as the file can get overwritten before it is
altered.

Please send any suggestions that might help, thankyou.

p.s. Some background on me, in case it helps. I don't know anything
about developing printer drivers, but i know C++ and am willing to try
driver development if necessary.
.