var textSlideSpeed = 500;       // Movement Duration measured (in ms)
var imgTransitionSpeed = 500;   // Fade Duration measured (in ms)
var imgShownLength = 3000;      // Image shown length (in ms)
var timerValue = 30;            // Timer interval (in ms)

var textHeight = 18;            // Text Slider Height
var maxTextTop = 299;           // Max Text Slider Top Location
var textTop = 299;              // Text Slider Top Location
var deltaY;                     // Calculated Delta-Y for text movement
var textInterval;               // Interval Container

var imgOpacity;                 // Image Opacity value
var deltaOpacity;               // Calculated Opacity transition for images
var imgInterval;                // Interval Container

var currentImage;               // Current Image Pointer

function startSlideShow() {
    imgOpacity = 100;
    deltaY = textHeight / textSlideSpeed * timerValue;
    deltaOpacity = imgOpacity / imgTransitionSpeed * timerValue;
    textHeight = 0;
    currentImage = 0;
    
    $get('galleryTop').style.backgroundImage = 'url(' + galleryList[currentImage][0] + ')';
    $get('imgTitle').innerHTML = galleryList[currentImage][1];
    currentImage += 1;
    if(currentImage == galleryList.length) currentImage = 0;
    $get('galleryBottom').style.backgroundImage = 'url(' + galleryList[currentImage][0] + ')';
    textInterval = setInterval('scrollUpText()', timerValue);
}

function scrollUpText() {
    textTop -= deltaY;
    textHeight = maxTextTop - textTop;
    $get('imgTitle').style.top = textTop + 'px';
    $get('imgTitle').style.height = textHeight + 'px';
    if(textTop <= 280) {
        textHeight = 18;
        clearInterval(textInterval);
        setTimeout('scrollDownText()', imgShownLength);
    }
}

function scrollDownText() {
    textTop += deltaY;
    textHeight = maxTextTop - textTop;
    $get('imgTitle').style.top = textTop + 'px';
    if(textHeight <= 0) textHeight = 0;
    $get('imgTitle').style.height = textHeight + 'px';
    if(textTop >= maxTextTop) {
        textTop = maxTextTop;
        textHeight = 0;
        imgInterval = setInterval('fadeImage()', timerValue);
    } else setTimeout('scrollDownText()', timerValue);
}

function fadeImage() {
    imgOpacity -= deltaOpacity;
    $get('galleryTop').style.opacity = imgOpacity/100;
	$get('galleryTop').style.filter = 'alpha(opacity=' + imgOpacity + ')';
    if(imgOpacity <= 0) {
        clearInterval(imgInterval);

        $get('galleryTop').style.backgroundImage = 'url(' + galleryList[currentImage][0] + ')';
        $get('imgTitle').innerHTML = galleryList[currentImage][1];
        imgOpacity = 100;
        $get('galleryTop').style.opacity = 1;
	    $get('galleryTop').style.filter = 'alpha(opacity=100)';
        
        currentImage += 1;
        if(currentImage == galleryList.length) currentImage = 0;
        $get('galleryBottom').style.backgroundImage = 'url(' + galleryList[currentImage][0] + ')';

        textInterval = setInterval('scrollUpText()', timerValue);
    }
}