// Improved Unobtrusive Javascript Image Rollover v1.0
// By Christian Watson: http://www.smileycat.com
// Based on a script by Chris Nott: http://www.dithered.com/javascript/rollovers/index.html
// license: http://creativecommons.org/licenses/by/1.0/

function isDefined(property) {
 return (typeof property != 'undefined');
}

var rolloverInitialized = false;
function rolloverInit() {

 if (!rolloverInitialized && isDefined(document.images)) {

 var bodyId = document.body.id; // ID of the BODY tag
 
 // get all images (including all <input type="image">s)
 // use getElementsByTagName() if supported
 var images = new Array();
 if (isDefined(document.getElementsByTagName)) {
 images = document.getElementsByTagName('img');
 var inputs = document.getElementsByTagName('input');
 for (var i = 0; i < inputs.length; i++) {
 if (inputs[i].type == 'image') {
 images[images.length] = inputs[i];
 }
 }
 }
 
 // otherwise, use document.images and document.forms collections
 // remove if not supporting IE4, Opera 4-5
 else {
 images = document.images;
 inputs = new Array();
 for (var formIndex = 0; formIndex < document.forms.length; formIndex++) {
 for (var elementIndex = 0; elementIndex < document.forms.elements.length; elementIndex++) {
 if (isDefined(document.forms.elements[i].src)) {
 inputs[inputs.length] = document.forms.elements[i];
 }
 }
 }
 }
 
 // get all images with '_off.' in src value excepting the one that is for the BODY

 for (var i = 0; i < images.length; i++) {
 if (images[i].src.indexOf('_off.') != -1) {

 // check for BODY image, and turn it 'on' if found
 if (images[i].src.indexOf(bodyId) != -1)
 images[i].src = images[i].src.replace(/_off\./, '_on.');
 else {

 var image = images[i];
 
 // store the off state filename in a property of the image object
 image.offImage = new Image();
 image.offImage.src = image.src;
 
 // store the on state filename in a property of the image object
 // (also preloads the on state image)
 image.onImage = new Image();
 image.onImage.imageElement = image;
 
 // add onmouseover and onmouseout event handlers once the on state image has loaded
 // Safari's onload is screwed up for off-screen images; temporary fix
 if (navigator.userAgent.toLowerCase().indexOf('safari') != - 1) {
 image.onmouseover = function() {
 this.src = this.onImage.src;
 };
 image.onmouseout = function() {
 this.src = this.offImage.src;
 };
 }
 else {
 image.onImage.onload = function() {
 this.imageElement.onmouseover = function() {
 this.src = this.onImage.src;
 };
 this.imageElement.onmouseout = function() {
 this.src = this.offImage.src;
 };
 };
 }
 
 // set src of on state image after defining onload event handler
 // so cached images (that load instantly in IE) will trigger onload
 image.onImage.src = image.src.replace(/_off\./, '_on.');

 }
 }
 }
 }
 rolloverInitialized = true;
}

// call rolloverInit when document finishes loading
if (isDefined(window.addEventListener)) {
 window.addEventListener('load', rolloverInit, false);
}
else if (isDefined(window.attachEvent)) {
 window.attachEvent('onload', rolloverInit);
}