-<div class="section">
-<h2>256-colour space</h2>
-<:
-for my $r (0 .. 5) {
- print '<table>';
- for my $g (0 .. 5) {
- print '<tr>';
- for my $b (0 .. 5) {
- my $index = $r*6*6 + $g*6 + $b + 16;
- print colcell($index, map { $_ && $_*40 + 55 } $r, $g, $b);
+ my $hmax = 2 * $dim * 3; # each face of the rgb cube
+ my $vmax = $dim - 1;
+ my $smax = $dim - 1;
+ $rgbval ||= sub { join('', @_), map { int $_ * 255 / $vmax } @_ };
+
+ my @greymap = @{$greyramp || []}; # [name, r, g=l, b]
+ my @colmap; # saturation => value => hue => [name, r,g,b]
+
+ for my $r (0 .. $dim - 1) {
+ for my $g (0 .. $dim - 1) {
+ for my $b (0 .. $dim - 1) {
+ my @rgb = ($r, $g, $b);
+
+ my ($h, $s, $v) = Shiar_Sheet::Colour->new(@rgb)->hsv;
+
+ if (!$s) {
+ if (@greymap) {
+ push @greymap, [ $rgbval->(@rgb) ];
+ next;
+ }
+
+ $h = 1; # greyscale hue
+ $s = $smax - $v + 1; # spread brightness over saturation groups
+ $v &&= $smax # highest saturation
+ or $v = $s = 1; # black at initial column
+ }
+
+ $h *= $hmax;
+ $v = $vmax - $v;
+ $s = $smax - $s - $v;
+
+ $colmap[$s][$v][$h] = [ $rgbval->(@rgb) ];
+ }