function setSwapImage(img) {
    var image_cache = new Object();
    var imgsrc = img.src;
    var dot = img.src.lastIndexOf('.');
    var imgsrc_on = img.src.substr(0, dot) + '_on' + img.src.substr(dot, 4);
    image_cache[img.src] = new Image();
    image_cache[img.src].src = imgsrc_on;
    $(img).hover(
      function() { img.src = imgsrc_on; },
      function() { img.src = imgsrc; }
    );
}

function initRollOverImages() {
  var image_cache = new Object();
  $("img.swap").each(function(i) {
  	setSwapImage(this);
  });
  $("input['image'].swap").each(function(i) {
  	setSwapImage(this);
  });
}


$(document).ready(initRollOverImages);