function makeOverlay(imageId, overlayId)
{
	var image = document.getElementById(imageId);
	var overlay = document.getElementById(overlayId);
	
	if(image && overlay)
	{
		var baseZ = 0;
		if(image.style.zIndex != "")
		{
			baseZ = image.style.zIndex;
		}
		
		overlay.position = "absolute";
		overlay.width = getElementWidth(image) + "px";
		overlay.height = getElementHeight(image) + "px";
		overlay.zIndex = baseZ + 1;
		image.parentNode.insertBefore(overlay, image.nextSibling);
		
		overlay.style.display = 'block';
	}
}

function getElementHeight(element) {
    return Math.max(
		element.scrollHeight,
		element.offsetHeight,
		element.clientHeight
		);
}

function getElementWidth(element) {
    return Math.max(
		element.scrollWidth,
		element.offsetWidth,
		element.clientWidth
		);
}