var pre_pictures = new Array(12);

for (i=0; i<12; i++) {
	pre_pictures[i] = new Image(487,332);
	pre_pictures[i].src = themepath + "petav2/headerimages/headerimg"+i+".jpg";
}

function initheader (startimg) {
	document.getElementById('img1').style.backgroundImage = "url('" + themepath + "petav2/headerimages/headerimg"+startimg+".jpg')";
	j=1;
	z=1;
	do {
		rn = Math.floor( Math.random() * 12);

	} while (startimg == rn);
	changeDelay();
}

function changeDelay () {
	if (j != 1) {
		do {
			rn_new = Math.floor( Math.random() * 12);
		} while (rn_new == rn);
		rn = rn_new;
	}
	window.setTimeout('changeImage()', 6000);
}

function changeImage() {
	if (j % 2 == 0) {
		document.getElementById('img1').style.opacity = 0;
		document.getElementById('img1').style.filter = "alpha(opacity=0)";
		document.getElementById('img1').style.backgroundImage = "url('" + themepath + "petav2/headerimages/headerimg"+rn+".jpg')";
		document.getElementById('img2').style.zIndex=1;
		document.getElementById('img1').style.zIndex=2;
		shiftOpacity('img1', 2000);
	}
	else {
		document.getElementById('img2').style.opacity = 0;
		document.getElementById('img2').style.filter = "alpha(opacity=0)";
		document.getElementById('img2').style.backgroundImage = "url('" + themepath + "petav2/headerimages/headerimg"+rn+".jpg')";
		document.getElementById('img1').style.zIndex=1;
		document.getElementById('img2').style.zIndex=2;
		shiftOpacity('img2', 2000);
	}


}

function opacity(id, opacStart, opacEnd, millisec) {
	//speed for each frame
	var speed = Math.round(millisec / 100);
	var timer = 0;

	//determine the direction for the blending, if start and end are the same nothing happens
	if(opacStart > opacEnd) {
	for(i = opacStart; i >= opacEnd; i--) {
	setTimeout("changeOpac(" + i + ",'" + id + "')",(timer * speed));
	timer++;
	}
	} else if(opacStart < opacEnd) {
	for(i = opacStart; i <= opacEnd; i++)
	{
	setTimeout("changeOpac(" + i + ",'" + id + "')",(timer * speed));
	timer++;
	}
	}
	j++;
	changeDelay();

}

//change the opacity for different browsers
function changeOpac(opacity, id) {
	var object = document.getElementById(id).style;
	object.opacity = (opacity / 100);
	object.MozOpacity = (opacity / 100);
	object.KhtmlOpacity = (opacity / 100);
	object.filter = "alpha(opacity=" + opacity + ")";
}

function shiftOpacity(id, millisec) {
	opacity(id, 0, 100, millisec);
}