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)
}

function trueSwapContent(pagina) {
	var contenido=document.getElementById("content");
	var img1=document.getElementById("imagen1");
	var img2=document.getElementById("imagen2");

	contenido.src=pagina + ".html";
	img1.style.backgroundImage= "url(images/av_06_" + pagina + ".jpg)";
	img2.style.backgroundImage= "url(images/av_07_" + pagina + ".jpg)";
}

function swapContent(pagina) {
	var contenido=document.getElementById("content");
	var img1=document.getElementById("imagen1");
	var img2=document.getElementById("imagen2");
	
	//speed for each frame
	var speed = Math.round(1000 / 100);
	var timer = 0;

	for(i = 100; i >= 0; i--) {
			setTimeout("changeOpac(" + i + ",'content')",(timer * speed));
			timer++;
		}

	setTimeout("trueSwapContent('" + pagina + "')",(timer * speed));
	timer=timer+100;
	
	for(i = 0; i <= 100; i++)
			{
			setTimeout("changeOpac(" + i + ",'content')",(timer * speed));
			timer++;
		}
		
}


function preloader() 
{
     // counter
     var i = 0;
     // create object
     imageObj = new Image();
     // set image list
     images = new Array();
     images[0]="images/av_01.gif"
     images[1]="images/av_02.gif"
     images[2]="images/av_03.jpg"
     images[3]="images/av_04.gif"
     images[4]="images/av_05.jpg"
     images[5]="images/av_08.gif"
     images[6]="images/CAMION.png"
     images[7]="images/av_07_electricos.jpg"
     images[8]="images/av_06_electricos.jpg"
     images[9]="images/av_06_electronicos.jpg"
     images[10]="images/av_07_electronicos.jpg"
     images[11]="images/av_07_mineria.jpg"
     images[12]="images/av_06_mineria.jpg"
	 images[13]="images/av_07_acerca.jpg"
     images[14]="images/av_06_acerca.jpg"
	 images[13]="images/CAMION_th.gif"
     images[14]="images/GEOREF_th.gif"
	 images[15]="images/GEOREF.gif"
	 images[16]="images/PROCES.gif"
	 images[17]="images/PROCES_th.gif"
	 
     // start preloading
     for(i=0; i<=17; i++) 
     {
          imageObj.src=images[i];
     }
}