Here's an example to get started.  Let's assume you have an image "mypic.jpg".

(1) djpeg -ppm mypic.jpg | gridpack -o /usr/local/www/data/gridpix/mypic.gpx

(2) Make sure you have CGI scripts with symlinks enabled on your web server.
    For Apache, you need something like

ScriptAlias /cgi-bin/ "/usr/local/www/cgi-bin/"

<Directory "/usr/local/www/cgi-bin">
    AllowOverride None
    Options ExecCGI FollowSymLinks
    Order allow,deny
    Allow from all
</Directory>

    in your /usr/local/etc/apache/httpd.conf file.

(3) Use a URL like this to refer to the image:

    http://hostname/cgi-bin/getimg2.cgi?mypic&720&576

    720 and 576 are the width and height of the GridPix window.  The default
    tile size is 144 by 144 so choose multiples of 144.

(4) To pop up a new window, use something like:

===
<script language="JavaScript">
<!--
function gridpix(pic) {
  window.open('/cgi-bin/getimg2.cgi?' + pic + '&720&576',
    'gridpix',
    'toolbar=no,status=yes,width=850,height=650,directories=no,scrollbars=no,location=no,resize=yes,menubar=no');
}
// -->
</script>
<a href="javascript:gridpix('mypic')">click here</a>
===

For more info, please read the documents in /usr/local/share/doc/gridpix.