// load in all images when page loads
function preloadHeaderImages()
{
	headerImageFiles = new Array();
	count = 0;
	for (image in headerImages){
		if (count > 0){
			headerImageFiles[count] = new Image();
			headerImageFiles[count].src = '/images/' + headerImages[currentHeaderImage][0];			
//			headerImageFiles[count].src = '/images/' + image[0];
			//alert(image + ',' + image[0] + ',' + image[1] + ',' + image[2]);
			//alert('Preload ' + '/images/' + image[0]);
		}
		count++;
	}
}

// wrapper function for changing image
function changeHeader()
{
	// move current image to background
	document.getElementById('header_image_path_1').src = '/images/' + headerImages[currentHeaderImage][0];
	
	// move along one in the array
	currentHeaderImage++;
	if (currentHeaderImage == headerImages.length){
		currentHeaderImage = 0;
	}
	
	// add in new information
	//document.getElementById('header_image_path_2').style.visibility = 'hidden';
	changeOpac(0, 'header_image_path_2');
	document.getElementById('header_image_path_2').src = '/images/' + headerImages[currentHeaderImage][0];
	//document.getElementById('header_image_path_2').style.visibility = 'visible';
	
	// begin transition and set end event
	opacity('header_image_path_2', 0, 100, 1000);
	setTimeout("changeHeaderFinish()", 750);
}

// finish change of header
function changeHeaderFinish(){

	document.getElementById('header_image_link').innerHTML = headerImages[currentHeaderImage][1];
	document.getElementById('header_image_href').href = headerImages[currentHeaderImage][2];
	document.getElementById('header_image_link').href = headerImages[currentHeaderImage][2];
	document.getElementById('header_image_more').href = headerImages[currentHeaderImage][2];

}

// function to gradually change the opacity
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++;
        }
    }
}

//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 + ")";
}