
Prologues and a few other PostScript files that are copied to /usr/lib/postscript
(ie. LIBDIR in ../Makefile) when you do an install.

Default settings for things like the linewidth in posttek and postbgi, have been
moved to these files. All can be changed without requiring a recompilation of any
programs supplied with this package. In addition all the translators understand
the -P option that lets you pass arbitrary PostScript through to the output file.
The option can be useful if you want to change parameters that are defined in
the prologue but not tied to specific command line options.

For example, the DMD bitmap translator (postdmd) that assumes a screen resolution
of 100 dpi. screenres is set to 100 in postdmd.ps, but there's no explicit option
to change it. If the bitmap resolution happened to be 300 dpi typing either,

	postdmd -P"/screenres 300 def" file

or,

	postdmd -P"/screenres 300" file

sets screenres to 300. In the first case the definition is made immediately after
the prologue, while in the second it's made when procedure setup is executed.

Another example is postbgi.ps, which can be used as the prologue for both STARE
and PRISM jobs. Although STARE (black and white) and PRISM (color) jobs are both
written in BGI, experience shows that PRISM jobs are often fundamentally different
and often require device specific tuning that's rarely needed for STARE jobs. The
prologue (postbgi.ps) defines a boolean called prism (initialized to false) while
the command line,

	postbgi -P"/prism true" file >file.ps

sets prism to true. What you end up getting is the device specific tuning needed
for most PRISM jobs.

