var current = 0;
function roll_background() {
	var total_nb_of_images = a_imgHome.length;

	var imgs = $$('img.background_image');
	
	if (imgs.first().visible() == true) {
		var old_image = imgs.first();
		var new_image = imgs.last();
	} else {
		var new_image = imgs.first();
		var old_image = imgs.last();
	}
	
	var old_bg = parseInt(old_image.readAttribute('current_pic'));

	var num_new_bg = (old_bg + 1) % total_nb_of_images;
	
	var new_img_url = a_imgHome[num_new_bg];

	preload_image(new_img_url);
	
	new_image.writeAttribute('src', new_img_url);
	new_image.writeAttribute('current_pic', num_new_bg);

	new Effect.Parallel([
		new Effect.Fade(old_image, { sync: true, duration: 1.5 }),
		new Effect.Appear(new_image, { sync: true, duration: 1.5 })
	], {
		duration: 3,
		afterFinish: function(){
			setTimeout("roll_background()",3000);
		}
	});
}



/*
function roll_background() {
	var total_nb_of_images = a_imgHome.length;

	var imgs = $$('img.background_image');
	
	if (imgs.first().visible() == true) {
		var old_image = imgs.first();
		var new_image = imgs.last();
	} else {
		var new_image = imgs.first();
		var old_image = imgs.last();
	}
	
	var old_bg = parseInt(old_image.readAttribute('current_pic'));

	var num_new_bg = (old_bg + 1) % total_nb_of_images;
	
	var new_img_url = a_imgHome[num_new_bg];

	preload_image(new_img_url);
	
	new_image.writeAttribute('src', new_img_url);
	new_image.writeAttribute('current_pic', num_new_bg);

	new Effect.Parallel([
		new Effect.Fade(old_image, { sync: true, duration: 1.5 }),
		new Effect.Appear(new_image, { sync: true, duration: 1.5 })
	], {
		duration: 3,
		afterFinish: function(){
			setTimeout("roll_background()",3000);
		}
	});
}
*/