123 lines
3.2 KiB
Perl
123 lines
3.2 KiB
Perl
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#!/usr/bin/perl
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#
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use strict;
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BEGIN {
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$PaletteModify::HAVE_CRC = eval "use String::CRC32 (); 1;";
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}
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package PaletteModify;
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sub common_alter
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{
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my ($palref, $table) = @_;
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my $length = length $table;
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my $pal_size = $length / 3;
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# tinting image? if so, we're remaking the whole palette
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if (my $tint = $palref->{'tint'}) {
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my $dark = $palref->{'tint_dark'};
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my $diff = [ map { $tint->[$_] - $dark->[$_] } (0..2) ];
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$palref = {};
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for (my $idx=0; $idx<$pal_size; $idx++) {
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for my $c (0..2) {
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my $curr = ord(substr($table, $idx*3+$c));
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my $p = \$palref->{$idx}->[$c];
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$$p = int($dark->[$c] + $diff->[$c] * $curr / 255);
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}
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}
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}
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while (my ($idx, $c) = each %$palref) {
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next if $idx >= $pal_size;
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substr($table, $idx*3+$_, 1) = chr($c->[$_]) for (0..2);
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}
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return $table;
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}
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sub new_gif_palette
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{
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my ($fh, $palref) = @_;
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my $header;
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# 13 bytes for magic + image info (size, color depth, etc)
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# and then the global palette table (3*256)
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read($fh, $header, 13+3*256);
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# figure out how big global color table is (don't want to overwrite it)
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my $pf = ord substr($header, 10, 1);
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my $gct = 2 ** (($pf & 7) + 1); # last 3 bits of packaged fields
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substr($header, 13, 3*$gct) = common_alter($palref, substr($header, 13, 3*$gct));
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return $header;
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}
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sub new_png_palette
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{
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my ($fh, $palref) = @_;
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# without this module, we can't proceed.
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return undef unless $PaletteModify::HAVE_CRC;
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my $imgdata;
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# Validate PNG signature
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my $png_sig = pack("H16", "89504E470D0A1A0A");
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my $sig;
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read($fh, $sig, 8);
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return undef unless $sig eq $png_sig;
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$imgdata .= $sig;
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# Start reading in chunks
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my ($length, $type) = (0, '');
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while (read($fh, $length, 4)) {
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$imgdata .= $length;
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$length = unpack("N", $length);
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return undef unless read($fh, $type, 4) == 4;
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$imgdata .= $type;
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if ($type eq 'IHDR') {
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my $header;
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read($fh, $header, $length+4);
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my ($width,$height,$depth,$color,$compression,
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$filter,$interlace, $CRC)
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= unpack("NNCCCCCN", $header);
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return undef unless $color == 3; # unpaletted image
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$imgdata .= $header;
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} elsif ($type eq 'PLTE') {
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# Finally, we can go to work
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my $palettedata;
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read($fh, $palettedata, $length);
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$palettedata = common_alter($palref, $palettedata);
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$imgdata .= $palettedata;
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# Skip old CRC
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my $skip;
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read($fh, $skip, 4);
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# Generate new CRC
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my $crc = String::CRC32::crc32($type . $palettedata);
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$crc = pack("N", $crc);
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$imgdata .= $crc;
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return $imgdata;
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} else {
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my $skip;
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# Skip rest of chunk and add to imgdata
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# Number of bytes is +4 becauses of CRC
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#
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for (my $count=0; $count < $length + 4; $count++) {
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read($fh, $skip, 1);
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$imgdata .= $skip;
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}
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}
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}
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return undef;
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}
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1;
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