#! /usr/bin/perl 
#
#   halftone.pl -- PostScript ファイルのハーフトーン周波数を変える
#
#	0.0: Jul. 22, 1999 by Dai ISHIJIMA (xv-ps-tombow.pl)
#	0.1: Jul. 27, 2000 (only halftone)
#
#   書式
#	perl halftone.pl [オプション] [< 入力ファイル] [> 出力ファイル]
#
#   オプション
#	-x 倍率		ハーフトーン周波数を
#			プリンタデフォルトの <倍率> 倍に設定する
#	-f 周波数	ハーフトーン周波数を <周波数> に設定する
#
#	Apple LaserWriter16/600PS2 では 106 lpi がデフォルト。
#	LaserPress 2100PS2 では 90 lpi。
#	LBP-B406PS では 30 lpi。
#
#	印刷できれいに仕上るのは、30〜90 ぐらい。60ぐらいが適当かも
#	- (もちろん印刷屋に依存するんだけど :-)
#

$halftone = "ABSOLUTE";
#$halftone = "RELATIVE";
$freq = 60;
#$freq = 1.0;


if ($ARGV[0] eq '-x') {
	$halftone = "RELATIVE";
	if ($ARGV[1] =~ /[.0-9][.0-9]*/) {
		$freq = $ARGV[1];
	}
	else {
		$freq = 1.0;
	}
}
elsif ($ARGV[0] eq '-f') {
	$halftone = "ABSOLUTE";
	if ($ARGV[1] =~ /[.0-9][.0-9]*/) {
		$freq = $ARGV[1];
	}
	else {
		print STDERR "halftone frequency required\n";
		exit 1;
	}
}

while (<STDIN>) {
	if (/^%%Page:/) {
		print ;
		print <<'EOF';

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% アミ点の細かさ
%/Halftone 1.0 def	% Halftone = 1 : プリンタのデフォルトを使う
%/Halftone 1.5 def	% Halftone > 1 : デフォルトより細かくする
%/Halftone 0.75 def	% Halftone < 1 : デフォルトより荒くする
% アミ点を細かくする or 荒くする
%currentscreen 3 2 roll Halftone mul 3 -2 roll setscreen
%currentscreen 3 2 roll pop 60 3 -2 roll setscreen
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
EOF
		if ($halftone eq "ABSOLUTE") {
			print "currentscreen 3 2 roll ";
			print "pop $freq ";
			print "3 -2 roll setscreen\n";
		}
		else {
			print "currentscreen 3 2 roll ";
			print "$freq mul ";
			print "3 -2 roll setscreen\n";
		}
		print <<'EOF';
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
EOF
	}
	else {
		print;
	}
}