From: Mischa POSLAWSKY <perl@shiar.org>
Date: Tue, 13 Oct 2009 16:00:09 +0000 (+0000)
Subject: termcol: adapt text colour to background luminosity
X-Git-Tag: v1.3~116
X-Git-Url: http://git.shiar.nl/sheet.git/commitdiff_plain/43f639f1fdbf9dd95236037d9291854559e92d92

termcol: adapt text colour to background luminosity

Ensure legibility by using white text on perceived dark backgrounds.
---

diff --git a/termcol.plp b/termcol.plp
index 3dd1d1b..e313856 100644
--- a/termcol.plp
+++ b/termcol.plp
@@ -3,6 +3,7 @@ use utf8;
 use strict;
 use warnings;
 use open IO => ':utf8';
+use List::Util 'min';
 
 our $VERSION = 'v1.0';
 
@@ -22,39 +23,67 @@ $header{content_type} = 'text/html; charset=utf-8';
 <h1>Terminal colours</h1>
 
 <table>
-<tr><th>#<td>xterm</tr>
 <:
+sub luminance {
+	# perceived brightness (using ITU-R recommendation 601 luma co-efficients)
+	my ($r, $g, $b) = @_;
+	return $r*.299 + $g*.587 + $b*.114;
+}
+
+sub colcell {
+	my $id = shift;
+	my @rgb = @_ >= 3 ? @_ : (map {hex} $_[0] =~ /(..)/g);
+	my $rgb24 = '';
+	$rgb24 .= sprintf '%X', min($_ / 17 + .5, 15) for @rgb[0..2];
+	my $rgb48 = '';
+	$rgb48 .= sprintf '%02X', $_ for @rgb[0..2];
+	my $inverse = sprintf('%X', luminance(@rgb)/255 < .3 ? 12 : 0) x 3;
+	return sprintf '<td style="%s; padding:0 1ex">%s<td style="%s">%s<td style="%s">%s',
+		"background:#$rgb48; color:#$inverse",
+		$id,
+		"background:#000; color:#$rgb48",
+		$rgb24,
+		"background:#FFF; color:#$rgb48",
+		$rgb24,
+}
+
 my %col = (
 	-name => [
-		qw/black red green orange blue magenta cyan gray
-		   gray red green yellow blue magenta cyan white/,
+		qw/black maroon green olive  navy purple  cyan silver
+		   gray  red    lime  yellow blue fuchsia aqua white/,
 		qw/reset bold dim italic underline blink fastblink
 		   reverse hidden/,
 	],
-	linux => [
-		qw/000 CCC/,
-		qw/000 A00 0A0 A50 00A A0A 0AA AAA
-		   555 F55 5F5 FF5 55F F5F 5FF FFF/,
+	html => [
+		qw/000000 CCCCCC/,
+		qw/000000 800000 008000 808000 000080 800080 008080 C0C0C0
+		   808080 FF0000 00FF00 FFFF00 0000FF FF00FF 00FFFF FFFFFF/,
+	],
+	cga => [
+		qw/000000 CCCCCC/,
+		qw/000000 AA0000 00AA00 AA5500 0000AA AA00AA 00AAAA AAAAAA
+		   555555 FF5555 55FF55 FFFF55 5555FF FF55FF 55FFFF FFFFFF/,
 	],
 	xterm => [
-		qw/000 CCC/,
-		qw/000 C00 0C0 CC0 4682B4 C0C 0CC E5E5E5
-		   4C4C4C F00 0F0 FF0 1E90FF F0F 0FF FFF/,
+		qw/000000 CCCCCC/,
+		qw/000000 CC0000 00CC00 CCCC00 4682B4 CC00CC 00CCCC E5E5E5
+		   4C4C4C FF0000 00FF00 FFFF00 1E90FF FF00FF 00FFFF FFFFFF/,
 	],
 	tango => [
-		qw/000 CCC/,
+		qw/000000 CCCCCC/,
 		qw/2E3436 CC0000 4E9A06 C4A000 3465A4 75507B 06989A D3D7CF
 		   555753 EF2929 8AE234 FCE94F 729FCF AD7FA8 34E2E2 EEEEEC/,
 	],
 );
 
+my @termlist = qw(html cga xterm tango);
+print '<tr>', (map {'<th colspan="3">'.$_} @termlist), "</tr>\n";
 for my $num (0 .. 15) {
-	printf('<tr><th>%d<td>%s%s</tr>'."\n",
-		$num,
-		$col{-name}[$num],
-		join('', map {sprintf '<td style="%s">&nbsp;▪&nbsp;',
-			'background:#'.$col{$_}[0].'; color:#'.$col{$_}[$num + 2],
-		} qw/linux xterm tango/ ),
+	printf('<tr>%s</tr>'."\n",
+		join('', map {
+			my $rgb = $col{$_}[$num + 2];
+			colcell($_ eq 'html' ? $col{-name}[$num] : $num, $rgb, $col{$_}[0])
+		} @termlist ),
 	);
 }
 :></table>