/*
 * The image dissolve effects code uses work presented by article entitled
 * "Cross-browser BlendTrans Filter JavaScript" on 
 * http://www.brainerror.net/scripts_js_blendtrans.php
 */
/*
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 changeOpac_reverse(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 blend_image(divid,imageid,elenco_img){

   	/*
	 * per controllare che non venga presa la stessa immagine 2 volte setto il valore di j in un campo, 
	 * lo recupero e lo confronto con quello appena calcolato
	 */
	var j_old = parseInt(document.getElementById('j_old').value);
	var singole_img = elenco_img.split(",");
	var numero_img = (singole_img.length);
	var j = parseInt(Math.floor(Math.random() * numero_img));
	while ( j == j_old ){
		var j = parseInt(Math.floor(Math.random() * numero_img));
	}
	document.getElementById('j_old').value = j;
	var image_file = singole_img[j];

	var speed = Math.round(1000 / 100);
    var timer = 0;

    //set the current image as background
	document.getElementById(divid).style.backgroundImage = "" + document.getElementById(imageid).style.backgroundImage + "";

    //make image transparent
    changeOpac(0, imageid);

    //make new image
	document.getElementById(imageid).style.backgroundImage = "url(" + image_file + ")";

    //fade in image
    for(i = 0; i <= 100; i++) {
        setTimeout("changeOpac(" + i + ",'" + imageid + "')",(timer * speed));
        timer++;
    }

	/*
    //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 = image_file;

    //fade in image
    for(i = 0; i <= 100; i++) {
        setTimeout("changeOpac(" + i + ",'" + imageid + "')",(timer * speed));
        timer++;
    }
	*/

}