/* fetch next image */
function nextImage(o) {
    do o = o.nextSibling;
    while(o && o.tagName != 'IMG');
    return o;
}

/* fetch first image inside an element */
function firstChildImage(o) {
    o = o.firstChild;
    while(o && o.tagName != 'IMG') {
        o = o.nextSibling;
    }
    return o;
}

//set the opacity of an element to a specified value
function setOpacity(obj, opac) {
    obj.style.opacity = (opac / 100);
    obj.style.MozOpacity = (opac / 100);
    obj.style.KhtmlOpacity = (opac / 100);
    obj.style.filter = 'alpha(opacity=' + opac + ')';
}

/* make image invisible and set next one as current image */
function getNextImage(image) {
    if(next = nextImage(image)) {
	image.style.display = 'none';
	image.style.zIndex = 0;

	next.style.display = 'block';
	next.style.zIndex = 100;
    } else {
	//if there is not a next image, get the first image again
	next = firstChildImage(image.parentNode);
    }
    return next;
}

/* set default values for parameters and starting image */
function blendImages(id, speed, pause, caption) {
    if(speed == null) {
        speed = 50;
    }
    
    if(pause == null) {
        pause = 2000;
    }

    var blend = document.getElementById(id);
    var image = firstChildImage(blend);

    startBlending(image, speed, pause, caption);
}

/* make image a block-element and set the caption */
function startBlending(image, speed, pause, caption) {
    image.style.display = 'block';

    if(caption != null) {
	document.getElementById(caption).innerHTML = image.alt;
    }

    continueFadeImage(image, 0, speed, pause, caption);
}

/* ASC: copied from http://www.sean.co.uk/a/webdesign/javascriptdelay.shtm */
function pausecomp(millis) {
    var date = new Date();
    var curDate = null;

    do { curDate = new Date(); }
    while(curDate-date < millis);
} 

/* set an increased opacity and check if the image is done blending */
function continueFadeImage(image, opacity, speed, pause, caption) {
    opacity = opacity + 3;

    if (opacity < 103) {
	setTimeout(function() {fadeImage(image, opacity, speed, pause, caption)}, speed);
    } else {
	/* if the image is done, set it to the background and make it transparent*/
	image.parentNode.style.backgroundImage = "url("+image.src+")";

	/* ASC: pause 1sec here to prevent MSIE image flash ... */
	var paws=pause-1000;
	if (paws < 0 ) {
		paws = 0;
	}
	pausecomp(1000);

	setOpacity(image,0);
	/* get the next image and start blending it again */
	image = getNextImage(image);
	setTimeout(function() {startBlending(image, speed, pause, caption)}, paws);		
    }
}

/* set the opacity to a new value and continue the fading */
function fadeImage(image, opacity, speed, pause, caption) {
    setOpacity(image,opacity);
    continueFadeImage(image, opacity, speed, pause, caption);
}