From d29916edd5f2af73164483662b5e49fdc6e3e697 Mon Sep 17 00:00:00 2001
From: Mischa POSLAWSKY <perl@shiar.org>
Date: Sat, 31 Oct 2015 21:14:44 +0100
Subject: [PATCH] termcol: list 256-colour hues starting with red
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Most wheels have red at 0° so having it on top is more familiar.
Coincidentally also avoids undesirable row breaks.
---
 Shiar_Sheet/Colour.pm | 7 +++++--
 termcol.plp           | 9 ++++-----
 2 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/Shiar_Sheet/Colour.pm b/Shiar_Sheet/Colour.pm
index cedfdfb..cdac0b3 100644
--- a/Shiar_Sheet/Colour.pm
+++ b/Shiar_Sheet/Colour.pm
@@ -4,7 +4,7 @@ use strict;
 use warnings;
 use List::Util qw( min max );
 
-our $VERSION = '1.02';
+our $VERSION = '1.03';
 
 # ITU-R recommendation 601 luma co-efficients
 our $kr = .299;
@@ -42,9 +42,12 @@ sub luminance {
 }
 
 sub hue {
+	# colour shift (red = 0 .. 1)
 	my ($r, $g, $b) = @{ $_[0] };
 	my $hue = atan2 sqrt(3) * ($g - $b), $r*2 - $g - $b;
-	return ($hue + $PI) / $PI / 2; # 0 .. 1
+	$hue /= $PI * 2;  # -.5 .. .5
+	$hue++ if $hue < 0;  # fp $hue %= 1
+	return $hue;
 }
 
 sub rgb24 {
diff --git a/termcol.plp b/termcol.plp
index 74bcbc4..5a4e83e 100644
--- a/termcol.plp
+++ b/termcol.plp
@@ -28,7 +28,7 @@ print
 
 <div class="section">
 <:
-use Shiar_Sheet::Colour '1.02';
+use Shiar_Sheet::Colour '1.03';
 use List::Util qw( min max );
 
 sub colcell {
@@ -259,18 +259,17 @@ for my $r (0 .. 5) {
 			my $index = $r*6*6 + $g*6 + $b + 16;
 			my @rgb = map { $_ && $_*40 + 55 } $r, $g, $b;
 
-			my $h = Shiar_Sheet::Colour->new(@rgb)->hue * 35;
+			my $h = Shiar_Sheet::Colour->new(@rgb)->hue * 33;
 			my $v = int(max(@rgb) / 255 * 5);
 			my $s = abs(min(@rgb) - max(@rgb)) / 255 * 7;
 			my $grey = !$s;
 
-			$h-- for grep {$h >= $_} 4, 6, 16, 19, 28, 31;
 			$v = 5 - $v;
 			$s = 7 - $s - $v;
 			$s-- if $s;
 
 			if ($grey) {
-				$h = 30;  # greyscale hue
+				$h = 33;  # greyscale hue
 				$s -= 2;  # lowest saturation for other hues
 				$v = $s = 0 if $s < 0;  # black at full saturation
 			}
@@ -283,7 +282,7 @@ for my $r (0 .. 5) {
 {
 	print '<table class=mapped>';
 	printf '<colgroup span=%d>', 3 * @{$_} for @colmap;
-	for my $h (0 .. 30) {
+	for my $h (grep { $colmap[0][0][$_] } 0 .. $#{ $colmap[0][0] }) {
 		print '<tr>';
 		print colcell(@$_) for map { $_->[$h] } map { @{$_} } @colmap;
 	}
-- 
2.30.0