#!/usr/local/bin/perl
# rlumin.pl - Generate color relative luminance chart
# Copyright 2015 David Meyer <papa@sdf.org> +JMJ
# (License and documentation at bottom of file.)
# Source: Ben Caldwell et al. ed. Web Content Accessibility
# Guidelines (WCAG) 2.0. World Wide Web Consortium (W3C).
# December 11, 2008.
# <http://www.w3.org/TR/2008/REC-WCAG20-20081211/>
# accessed January 7, 2015.
use strict;
use warnings;
our %bytesc = (
0 => 0,
17 => 1,
68 => 4,
119 => 7,
187 => 11,
255 => 15
);
our(@color, %rlumin);
sub colorsc {
my($r, $g, $b) = @_;
return sprintf("#%x%x%x", $bytesc{$r}, $bytesc{$g}, $bytesc{$b});
}
sub lumc {
my($c) = @_;
my $cn = $c/255;
if ($cn <= .03928) {return $cn/12.92;}
else {return (($cn+.055)/1.055)**2.4;}
}
sub rlumin {
my($r, $g, $b) = @_;
return .2126 * lumc($r) + .7152 * lumc($g) + .0722 * lumc($b);
}
our($r, $g, $b);
for $r (0, 17, 68, 119, 187, 255) {
for $g (0, 17, 68, 119, 187, 255) {
for $b (0, 17, 68, 119, 187, 255) {
my $colorsc = colorsc($r, $g, $b);
push @color, $colorsc;
$rlumin{$colorsc} = rlumin($r, $g, $b);
}
}
}
our @lcolor = sort {$rlumin{$a} <=> $rlumin{$b}} @color;
print "<body style='background-color:#555;color:#fff;'>\n<ol>\n";
for my $c (@lcolor) {
my $fg = $rlumin{$c} < .35 ? '#fff' : '#000';
print "<li style='background-color:$c;margin:2px;padding:10px;'><span style='color:$fg;'>$c $rlumin{$c}</span></li>\n";
}
print "</ol>\n</body>\n";
exit 0
__END__
# Documentation #####################################################
=head1 NAME
template.pl - Perl script template (command line)
=head1 SYNOPSIS/USAGE
=head1 DESCRIPTION
Mark up code elements with C<>, file names with F<> (or C<> for
readability), command names with B<>. Also I<> for italics, U<> for
underline. Entities: E<lt> ('<'), E<gt> ('>').
=head1 OPTIONS
=item B<-o> I<value>, B<--option>=I<value>
=head1 RETURN VALUE
=head1 ERRORS
=head1 DIAGNOSTICS
=head1 EXAMPLES
=head1 ENVIRONMENT
=over 6
=item VARIABLE
Description of usage of environment variable C<VARIABLE>.
=back
=head1 FILES
=head1 BUGS, LIMITATIONS, AND CAVEATS
=head1 NOTES
=head1 AUTHOR
David Meyer <papa@sdf.org>
=head1 HISTORY
=head1 COPYRIGHT AND LICENSE
Copyright 201x David Meyer
=head1 SEE ALSO
# Emacs control #####################################################
#Local variables:
#mode: perl
#End: