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#!/usr/bin/perl
# Syntax: makescale left.pgm right.pgm > matrix.pgm
sub loadhistogram {
local ($filename,*array) = @_;
local ($i, $skip);
open HISTOGRAM, "pgmhist $filename |" ||
die "Can't run 'pgmhist $filename'\n";
for (0..255) {
@array[$_] = 0;
}
$i = <HISTOGRAM>;
while (<HISTOGRAM>) {
chop;
@words = split;
$array[$words[0]] = $words[1];
}
close HISTOGRAM;
}
sub sumhistogram {
local(*array) = @_;
local ($minval, $maxval, $i);
$minval = 0;
while ($minval < 255 && $array[$minval] == 0) {
$minval ++;
}
$maxval = 255;
while ($maxval >= $minval && $array[$maxval] == 0) {
$maxval --;
}
for (1 .. 255) {
$array[$_] += $array[$_ - 1];
}
return ($minval, $maxval);
}
loadhistogram($ARGV[0], *leftarray);
loadhistogram($ARGV[1], *rightarray);
($leftmin, $leftmax) = sumhistogram(*leftarray);
($rightmin, $rightmax) = sumhistogram(*rightarray);
$leftresidue = 255 - $leftmax;
$rightresidue = 255 - $rightmax;
for (0 .. $rightmin - 1) {
$xlate[$_] = int (($leftmin * $_) / $rightmin);
}
for ($rightmax + 1 .. 255) {
$xlate[$_] = int($leftmax + ($leftresidue * ($_ - $rightmax)) / $rightresidue);
}
$hit = $leftmin;
for ($rightmin .. $rightmax) {
while ($hit < $leftmax && $rightarray[$_] > $leftarray[$hit]) {
$hit ++;
}
$xlate[$_] = $hit;
}
print "P2\n256 1 255\n";
for (0..255) {
print "$xlate[$_]\n";
}
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