var theme_dir = 'themes/default/';

var loadingImg = new Image();
loadingImg.src = theme_dir + 'images/loading.gif';

var objBg = '';
var newBg = new Image();

var availableImgs = new Array();
var currentImg = 2;

availableImgs[0] = 'bg-left.jpg';
availableImgs[1] = 'bg-left2.jpg';
availableImgs[2] = 'bg-left3.jpg';
availableImgs[3] = 'bg-left4.jpg';

function bgSwitch(id, direction) {
	objBg = document.getElementById(id);
	
	objBg.style.backgroundImage = "url('" + loadingImg.src + "')";
	
	if (direction == 'n') {
		currentImg++;
		
		if (currentImg > availableImgs.length - 1) {
			currentImg = 0;
		}
	} else if (direction == 'p') {
		currentImg--;
		
		if (currentImg < 0) {
			currentImg = availableImgs.length - 1;
		}
	}
	
	newBg.onload = function () {
		objBg.style.backgroundImage = "url('" + newBg.src + "')";
	}
	
	setTimeout("preloadImg(" + currentImg + ")", 500);
	
	return false;
}

function preloadImg(imgNumber) {
	newBg.src = theme_dir + 'images/' + availableImgs[imgNumber];
}