#!/usr/bin/perl

# Usage: perl flip.pl inputfile.ps > outputfile.ps

# Very first attempt at flipping postscript pages. Useful for transparencies if
# you want to write on the opposite side to the printer ink.
# Iain Murray Nov 2003 -- www.iainmuray.net
# 
# Disclaimer, I know very little about postscript. Do let me know how this
# "should" be done. This doesn't work on many documents. Sometimes it does after
# if you run through ps2ps first.

while (<>) {
	if ((/^%%(HiRes|Page|)BoundingBox:/) && !(/\(atend\)/)) {
		# Fix up bounding box so it still covers everything
		# after flipping in the line y=0.
		chomp;
		($bb,$x1,$y1,$x2,$y2) = split(" ",$_);
		print $bb.' -'.$x2.' '.$y1.' -'.$x1.' '.$y2."\n";
	} else {
		print;
	}
	# Assume I can safely put a global flip after every page start.
	# Big assumption.
	# TODO sometimes works better if goes after EndPageSetup
	# Placing of this command really needs to be much more intelligent.
	if (/^%%Page:/) {
		print "-1.000 1.000 scale\n";
	}
}