var Rollovers = function(opt){
  var o = opt;
  var load = function() {
    $A(o.selector).each(function(s) {
      $$(s).each(
        function(i) {
          var os = i.src, ni = document.createElement('img');
          $(i).observe('mouseout', function(e){i.src = os;});
          ni.src = o.srcFunction(i,o);
          i.observe('mouseover', function(e){i.src = ni.src;});
        }
      );
    });
  };
  if(window.FastInit) {
  	FastInit.addOnLoad(load);
  } else {
  	Event.observe(window, 'load', load);
  }
}
Rollovers({
  selector : ['img.rollover'],
  srcFunction : function(i, o) {
    return i.src.replace(/(.*)\.(jpg|gif|png)$/i, "$1-rollover.$2");
  }
});