source: git/lib/make-pixel-font @ 583c17d

#!/usr/bin/perl
use warnings;
use strict;

my %bitno = (0 => 0);
for (0 .. 31) {
    $bitno{1 << $_} = $_;
}

my $last_ch = -1;
open U, '<', '/usr/share/unifont/unifont.hex' or die $!;
open O, '>', 'unifont.pixelfont' or die $!;
while (<U>) {
    my ($ch, $hex) = /^([[:xdigit:]]+):([[:xdigit:]]+)$/;
    if (!defined $ch) {
        print "Bad line: $_";
        next;
    }
    $ch = hex($ch);
#    print "$ch:\n";

    while (++$last_ch < $ch) {
        # print "Missing entry for ".($last_ch - 1 )."\n";
        print O pack 'C', 0x00;
    }

    # $len is 0, 2 or 4
    my $len = length($hex) / 16;
    my $packcode;
    if ($len == 4) {
        $packcode = 'n';
    } elsif ($len == 2) {
        $packcode = 'C';
    } elsif ($len == 0) {
        $packcode = '';
    } else {
        die "No handling for len = $len\n";
    }
    my $data = '';
    my $start;
    my $n = 0;
    my $pixels_set = 0;
    my $width = $len * 4;
    if ($len) {
        my @data = ();
        for (0 .. 15) {
            my $c = substr($hex, (15 - $_) * $len, $len);
            my $row = hex($c);
            $pixels_set |= $row;
            if (!defined $start) {
                # Skip blank rows at the bottom.
                next unless $row;
                $start = $_;
            }
            $n = $_ if $row;
            push @data, $row;

#       my $b = sprintf $fmt, $row;
#       $b =~ y/01/ @/;
#       print "\t$b\n";
        }

        my $left_gap = 0;
        my $lsb_used = $pixels_set & -$pixels_set;
        my $msb_used = 1 << ($len * 4 - 1);
        while ($msb_used > $pixels_set) {
            $msb_used >>= 1;
            ++$left_gap;
        }
        $data = join '', map {pack($packcode, $_ << $left_gap)} @data;
        my $right_gap = $bitno{$lsb_used} + $left_gap;
        $right_gap = 0 if ($left_gap == 16);
        $width -= $right_gap;
    } else {
        $width -= 2;
    }

    if (!defined $start) {
        # No set pixels.
        print O pack 'C', ($len * 4 - 4);
        die "not really empty!" unless $hex =~ /^0*$/;
    } else {
        die "really empty!" if $hex =~ /^0*$/;
        $n = $n + 1 - $start;
        print O pack 'C', (($len / 2) << 6) | $width;
        print O pack 'C', ($start << 4) | ($n - 1);
        die "too little data (".length($data)." < ".$n."*".($len/2).")" if length($data) < $n * $len/2;
        print O substr($data, 0, $n * $len / 2);
    }
}
close O or die $!;