termcol: lay out 256-colour table by h/s/v

[sheet.git] / Shiar_Sheet / Colour.pm

diff --git a/Shiar_Sheet/Colour.pm b/Shiar_Sheet/Colour.pm
index 7ea68e9dcf63bd3874facf8e8a89f068d52ba213..cedfdfb9e31aa722ff8027657fba1b97c455fb26 100644 (file)
--- a/Shiar_Sheet/Colour.pm
+++ b/Shiar_Sheet/Colour.pm
@@ -4,13 +4,15 @@ use strict;
 use warnings;
 use List::Util qw( min max );
 
-our $VERSION = '1.01';
+our $VERSION = '1.02';
 
 # ITU-R recommendation 601 luma co-efficients
 our $kr = .299;
 our $kb = .114;
 our $kg = 1 - $kb - $kr;
 
+my $PI = 2 * atan2 1, 0;
+
 sub new {
        my $class = shift;
        my @rgb = @_ >= 3 ? @_ : (map {hex} $_[0] =~ /(..)/g);
@@ -39,6 +41,12 @@ sub luminance {
        return $r*$kr + $g*$kg + $b*$kb;
 }
 
+sub hue {
+       my ($r, $g, $b) = @{ $_[0] };
+       my $hue = atan2 sqrt(3) * ($g - $b), $r*2 - $g - $b;
+       return ($hue + $PI) / $PI / 2; # 0 .. 1
+}
+
 sub rgb24 {
        my $str = '';
        $str .= sprintf '%X', min($_ / 17 + .5, 15) for @{ $_[0] };