// BlendTrans script by Des
// http://www.brainerror.net/scripts_js_blendtrans.php
// MRV: added use of IE blendTrans filter if available (smoother transition)
// MRV: 2008/12/09 removed use of IE blendTrans filter to enable usage
// with images of differing sizes. Added use of extra DIV containing image
// as an opacity-alteration target rather than the IMG node itself

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 unblendimage(divid, imageid, imagedivid) {
  // Setting opacity to 100% causes the background image to be briefly
  // visible on Win/Firefox. As a workaround, we set the background
  // equal to the foreground before setting opacity to 100%.
  if (!imagedivid) imagedivid=imageid;
  var el = document.getElementById(divid);
  var el2 = document.getElementById(imageid);
  el.style.backgroundImage = "url(" + el2.src + ")";
  changeOpac(100, imagedivid);
}

function blendimage(divid, imageid, imagefile, millisec, imagedivid) {
  if (!imagedivid) imagedivid=imageid;
  var el = document.getElementById(divid);
  var el2 = document.getElementById(imageid);
  if (!millisec) {
    el2.src = imagefile;
    el.style.backgroundImage = "url(" + imagefile + ")";
  } else {
    // Use Des' blendtrans
    //set the current image as background
    el.style.backgroundImage = "url(" + el2.src + ")";
    //make image transparent
    changeOpac(0, imagedivid);
    //make new image. Use delay so as to prevent flicker
    setTimeout("document.getElementById('"+imageid+"').src='"+imagefile+"'",(1*millisec/100));
    //fade in image
    var i;
    for(i = 2; i <= 99; i++) {
      setTimeout("changeOpac(" + i + ",'" + imagedivid + "')",(i*millisec/100));
    }
    setTimeout("unblendimage('"+divid+"','"+imageid+"','"+imagedivid+"')", millisec);
  }
}

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)
}