var timer;
var nextImageNumber;

function resetSlideTimer()
{
    clearInterval(timer);
    timer = setInterval('slideImg(' + nextImageNumber + ');', 6000);
}

function slideImg(imgIndex, value)
{
    if (value == null)
    {
        value = 10;
    }

    imgObj = document.getElementById('slide_img');
    if (value > 0)
    {
        changeOpacity(imgObj, value);
    }
    else if (value < 0)
    {
        negValue = value * -1;
        changeOpacity(imgObj, negValue);
    }
    else
    {
        changeImg(imgObj, imgIndex);
    }

    if (value > -10)
    {
        value--;
        setTimeout('slideImg(' + imgIndex + ',' +  value + ')', 35);
    }

    resetSlideTimer();
}

function preloadSlides()
{
    var images = ['images/slide1.jpg',
                  'images/slide2.jpg',
                  'images/slide3.jpg',
                  'images/slide4.jpg',
                  'images/slide5.jpg'];

    for (i=0; i < 5; i++)
    {
        image = new Image();
        image.src = images[i];
    }

    nextImageNumber = '2';
    timer = setInterval('slideImg(' + nextImageNumber + ');', 6000);
}

function changeImg(imgObj, imgIndex)
{
    var images = ['images/slide1.jpg',
                  'images/slide2.jpg',
                  'images/slide3.jpg',
                  'images/slide4.jpg',
                  'images/slide5.jpg'];

    imgObj = document.getElementById('slide_img');
    imgSrc = imgObj.src;
    imgObj.src = images[imgIndex - 1];

    oldNumber = imgSrc.charAt(imgSrc.length - 5);

    oldLink = document.getElementById('slide_link' + oldNumber);
    oldLink.style.backgroundImage = 'url(images/slide-link-inactive.png)';

    newLink = document.getElementById('slide_link' + imgIndex);
    newLink.style.backgroundImage = 'url(images/slide-link-active.png)';

    nextImageNumber = imgIndex + 1;

    if (nextImageNumber == 6)
    {
        nextImageNumber = 1;
    }
    nextImageNumber = nextImageNumber.toString();
}

function changeOpacity(imgObj, value)
{
    imgObj.style.opacity = value/10;
    imgObj.style.filter = 'alpha(opacity=' + value*10 + ')';
}