var margin = 0;
var dir = 0;
var overflow = -1;

var maxPics = 6;
var picArray = new Array();
var picId = 0;
var picSrcPre = "materials/scrolls/";
var picSrcPost = ".jpg";

function PreLoad() {
	for (var i = 0; i < maxPics; i++) {
		picArray[i] = new Image();
		picArray[i].src = picSrcPre + (i + 1) + picSrcPost;
	}
}

function Scroll() {
	if (overflow == -1) {
		overflow = document.getElementById("p_pic").width - 520;
	}
	if (dir == 0) {
		margin--;
		if (margin < (0 - overflow)) {
			ChangePic(dir);
			dir = 1;
		} else {
			document.getElementById('p_pic').style.marginLeft = margin + 'px';
		}
	} else {
		margin++;
		if (margin > 0) {
			ChangePic(dir);
			dir = 0;
		} else {
			document.getElementById('p_pic').style.marginLeft = margin + 'px';
		}
	}
	window.setTimeout("Scroll();", 60);
}

function ChangePic(get_dir) {

	var oldId = picId;
	while (oldId == picId) {
		picId = parseInt(Math.random() * maxPics - 1);
	}

	document.getElementById('p_pic').src = picArray[picId].src;

	overflow = picArray[picId].width - 520;

	document.getElementById('p_pic').style.width = picArray[picId].width + 'px';
	
	if (get_dir == 0) {
		margin = (0 - overflow);
	} else {
		margin = 0;
	}
	document.getElementById('p_pic').style.marginLeft = margin + 'px';
}