//Image slideshow with caption and alt tag
//Add <img id="slide"  src="imagename"/> and <p id="slideCaption">imageCaption</p> in the body

var previous=0; 


function viewSlideshow() {
	var images = new Array();
	var number = 0;
	var increment=0;
    
	images[number] = "images/feature/Pres_Khator_speaking_to_1301_Class.jpg";
	images[number++] = "images/feature/KhatorClassroom.jpg";
	
	images[number++] = "images/feature/ValentiSOC_Logo1.jpg";
	images[number++] = "images/feature/ValentiSOC_Logo2.jpg";
	images[number++] = "images/feature/ValentiSOC_Logo3.jpg";
	
	/*images[number++] = "images/feature/IABCphoto1.jpg";
	  images[number++] = "images/feature/IABCphoto2.jpg";
	  images[number++] = "images/feature/IABCphotos3.jpg";*/
	
	images[number++] = "images/feature/jjvsoc_letters1.jpg";
	images[number++] = "images/feature/jjvsoc_letters2.jpg";
    
	
	//images[number++] = "images/feature/UHVperspective1.jpg";    
	images[number++] = "images/feature/template_featureimage.jpg";
	images[number++] = "images/feature/vinyljjvsocbanner.jpg";
	images[number++] = "images/feature/khator.jpg";
	images[number++] = "images/feature/Valenti_SOC.jpg";
	
	
	var altTags = new Array();
	number = 0;
    
    altTags[number] = "Pres. Khator speaking to Prof. Keith Houk's 1301 Media and Society course the first week of classes";    
	altTags[number++] = "Pres. Khator handshakes Prof. Keith Houk - 1301 Media and Society professor the first week of classes";
	
	altTags[number++] = "Jack J. Valenti School of Communication Hanging Banner 1";
	altTags[number++] = "Jack J. Valenti School of Communication Hanging Banner 2";
	altTags[number++] = "Jack J. Valenti School of Communication Hanging Banner 3";
	  
	/*altTags[number++] = "IABC Hanging Banner";
	  altTags[number++] = "IABC Hanged Banner";
	  altTags[number++] = "IABC Hanged Banner"; */
	
	
	altTags[number++] = "Jack J. Valenti School of Communication's lettering 1 ";
	altTags[number++] = "Jack J. Valenti School of Communication's lettering 2";
		
	//altTags[number++] = "Jack J. Valenti School of Communication's perspective";
	altTags[number++] = "Jack J. Valenti's photo";
	altTags[number++] = "Jack J. Valenti School of Communication's vinyl banner";
	altTags[number++] = "President Khator visiting Jack J. Valenti School of Communication's classroom";
	altTags[number++] = "Jack J. Valenti photo";
	
	
	increment = Math.floor(Math.random() * (number+1));
	while ( increment == previous ) {
	  increment = Math.floor(Math.random() * (number+1));
	}
	previous=increment; 
	var img = document.getElementById("blendimage");
	img.alt = altTags[increment].toString();
	var pathImg=images[increment].toString();
	
	blendimage("blenddiv","blendimage",pathImg,3000);
}

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(1, 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)
}