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 3dd1d1b648b00c16f5adea532b542760f1ab41fa..e313856d44c8959717878e2f64c81e2bacaffdc6 100644 (file)
--- a/termcol.plp
+++ b/termcol.plp
@@ -3,6 +3,7 @@ use utf8;
 use strict;
 use warnings;
 use open IO => ':utf8';
 use strict;
 use warnings;
 use open IO => ':utf8';

+use List::Util 'min';

 
 our $VERSION = 'v1.0';
 
 
 our $VERSION = 'v1.0';
 


@@ -22,39 +23,67 @@ $header{content_type} = 'text/html; charset=utf-8';
 <h1>Terminal colours</h1>
 
 <table>
 <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 => [
 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/,
        ],
                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 => [
        ],
        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 => [
        ],
        tango => [

-               qw/000 CCC/,
+               qw/000000 CCCCCC/,

                qw/2E3436 CC0000 4E9A06 C4A000 3465A4 75507B 06989A D3D7CF
                   555753 EF2929 8AE234 FCE94F 729FCF AD7FA8 34E2E2 EEEEEC/,
        ],
 );
 
                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) {
 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>
        );
 }
 :></table>