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 = 0;

    //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)
}