// Globals
var intMaxFileNum = 16;
var divid = 'blenddiv';
var imageid = 'blendimage';
var intFileNum = Math.ceil(Math.random()*intMaxFileNum);
var displaySecs = 5;
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 + ")"; 
} 

function shiftOpacity(id, millisec) { 
    //if an element is invisible, make it visible, else make it ivisible 
    if(document.getElementById(id).style.opacity == 0) { 
        opacity(id, 0, 100, millisec); 
    } else { 
        opacity(id, 100, 0, millisec); 
    } 
} 

function blendimage(divid, imageid, imagefile, millisec) { 
    var speed = Math.round(millisec / 100); 
    var timer = 1; 
     
    //set the current image as background 
    document.getElementById(divid).style.backgroundImage = "url(" + document.getElementById(imageid).src + ")"; 
     
    //make image transparent 
    changeOpac(0, imageid); 
     
    //make new image 
    document.getElementById(imageid).src = imagefile; 

    //fade in image 
    for(i = 0; i <= 100; i++) { 
        setTimeout("changeOpac(" + i + ",'" + imageid + "')",(timer * speed)); 
        timer++; 
    } 
}

function currentOpac(id, opacEnd, millisec) { 
    //standard opacity is 100 
    var currentOpac = 100; 
     
    //if the element has an opacity set, get it 
    if(document.getElementById(id).style.opacity < 100) { 
        currentOpac = document.getElementById(id).style.opacity * 100; 
    } 

    //call for the function that changes the opacity 
    opacity(id, currentOpac, opacEnd, millisec) 
} 

var slideCache = new Array(); 
function RunSlideShow() { 
	if(intFileNum < intMaxFileNum) {
		intFileNum++;
	} else {
		intFileNum = 1;
	}
	var nextImage = '/images/upper_left_'+intFileNum+'.jpg';
	
	changeOpac(0, imageid); 
	blendimage(divid,imageid,nextImage,1000); 
	
	setTimeout("RunSlideShow()",displaySecs*1000); 
	
	// Cache the next image to improve performance. 
	var nextImage = '/images/upper_left_'+intFileNum+'.jpg';
	if (slideCache[nextImage] == null) { 
		slideCache[nextImage] = new Image; 
		slideCache[nextImage].src = nextImage; 
	} 
}