Image rollover snippets in Dreamweaver cc add transition

<a href="#" onMouseOut="MM_swapImgRestore()"     onMouseOver="MM_swapImage('porsche_356','','assets/porsche_356_sabbiatura_dopo_300x200.jpg',1)">

<img src="assets/porsche_356_sabbiatura_prima_300x200.jpg" alt="" width="300" height="200" class="img-lavorazioni" id="porsche_356"></a>

<script>

function MM_swapImgRestore() { //v3.0

  var i,x,a=document.MM_sr; for(i=0;a&&i<a.length&&(x=a)&&x.oSrc;i++) x.src=x.oSrc;

}

function MM_preloadImages() { //v3.0

  var d=document; if(d.images){ if(!d.MM_p) d.MM_p=new Array();

    var i,j=d.MM_p.length,a=MM_preloadImages.arguments; for(i=0; i<a.length; i++)

    if (a.indexOf("#")!=0){ d.MM_p=new Image; d.MM_p[j++].src=a;}}

}

function MM_findObj(n, d) { //v4.01

  var p,i,x;  if(!d) d=document; if((p=n.indexOf("?"))>0&&parent.frames.length) {

    d=parent.frames[n.substring(p+1)].document; n=n.substring(0,p);}

  if(!(x=d)&&d.all) x=d.all; for (i=0;!x&&i<d.forms.length;i++) x=d.forms;

  for(i=0;!x&&d.layers&&i<d.layers.length;i++) x=MM_findObj(n,d.layers.document);

  if(!x && d.getElementById) x=d.getElementById(n); return x;

}

function MM_swapImage() { //v3.0

  var i,j=0,x,a=MM_swapImage.arguments; document.MM_sr=new Array; for(i=0;i<(a.length-2);i+=3)

   if ((x=MM_findObj(a))!=null){document.MM_sr[j++]=x; if(!x.oSrc) x.oSrc=x.src; x.src=a[i+2];}

}

</script>

this is the test published:

https://alessiopaolettidesign.it/sabbiaturapg/