// navigation switch mouseover javascript
window.onload = mouseOverInit;

function mouseOverInit() {
	for (var i=0; i<document.links.length; i++) {
		var linkObj = document.links[i];
		if (linkObj.className) {
			var imgObj = document.getElementById(linkObj.className);
			if (imgObj) {
				setupRollover(linkObj, imgObj);
			}
		}
	}
}

function setupRollover(thisLink, centerKnobImg) {
	thisLink.imgToChange = centerKnobImg;
	thisLink.onmouseout = mouseOut;
	thisLink.onmouseover = mouseOver;	
	
	thisLink.outImage = new Image();
	thisLink.outImage.src = centerKnobImg.src;

	thisLink.overImage = new Image();
	thisLink.overImage.src = "images/nav/" + thisLink.id + ".png";
}

function mouseOver() {
	this.imgToChange.src = this.overImage.src;
}

function mouseOut() {
	this.imgToChange.src = this.outImage.src;
}

// preload navigation images
var preloaded = new Array();
function preload_images() {
    for (var i = 0; i < arguments.length; i++) {
        preloaded[i] = document.createElement('img');
        preloaded[i].setAttribute('src', arguments[i]);
    };
};

preload_images (
	'images/nav/knob_center_left.png',
	'images/nav/knob_center_right.png',
	'images/nav/knob_on.png',
	 
	'images/nav/news_on.png',
	'images/nav/contact_on.png'
);