#!/usr/bin/perl

# pixel.cgi -- Generate a single-pixel GIF of a given color.
#
# Usage:
#  <img src="pixel.cgi/CC9966.gif" width=25 height=25>
#
# Dave W. Smith <dws@davewsmith.com>

my($rgb) = $ENV{PATH_INFO} =~ m|/([0-9A-Za-z]{6})(?:\.gif)?$|i;
$rgb ||= '888888';

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;

[download]

In reply to On-demand single-pixel GIFs by dws

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.