http://www.perlmonks.org?node_id=146130


in reply to On-demand single-pixel GIFs

I worked out a slighlty modified version of the great and really useful code above. I added support for 3 hex colors and changed default behavior to exit if no $rgb is matched.
use strict; my($rgb) = $ENV{PATH_INFO} =~ m|/([0-9A-F]+)(?:\.gif)?$|i; grep {length $rgb == $_} (3, 6) || exit; $rgb = join '', map { $_ x 2 } $rgb =~ /./g if length( $rgb ) == 3; my $gif = pack("H*", '47494638396101000100B30000' . $rgb . 'FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF' . 'FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF' . 'FFFFFFFFFFFFFFFFFFFFFFFFFF2C0000' . '0000010001000004021044003B' ); binmode(STDOUT); print "Content-type: image/gif\r\n"; print "Content-length: ", length($gif), "\r\n"; print "\r\n"; print $gif;
$|=$_='1g2i1u1l2i4e2n0k',map{print"\7",chop;select$,,$,,$,,$_/7}m{..}g