// Author: AdScience

var iPreloads = new Array();

function iPreload(srcName, imgName) {
	var imgOver = new Image();
	imgOver.src = iOverSrc(srcName);
	iPreloads[imgName] = imgOver;
}

function iOverSrc(srcName) {
	var ext = srcName.lastIndexOf(".");
	return srcName.substring(0, ext) +
			"-ovr" +
			srcName.substring(ext, srcName.length);
}

function iRolOvr(imgName) {
	var img = document.images[imgName];
	if (img) {
		img.out = img.src;
		img.src = iPreloads[imgName].src;
	}
}

function iRolOut(imgName) {
	var img = document.images[imgName];
	if (img.out) {
		img.src = img.out;
	}
}