var Fondu = function(classe_img){
        this.courant = 0;
        this.coeff = 100;
        this.collection = this.getImages();
        this.collection[0].style.zIndex = 100;
        this.total = this.collection.length - 1;
        this.encours = false;
}
Fondu.prototype.getImages = function(){
        var tmp = [];
        if(document.getElementsByClassName){
                tmp = document.getElementsByClassName('imgarriereplan');
        }else{
                var i=0;
                while(document.getElementsByTagName('*')[i]){
                        if(document.getElementsByTagName('*')[i].className=='imgarriereplan'){
                                tmp.push(document.getElementsByTagName('*')[i]);
                        }
                        i++;
                }
        }
        var j=tmp.length;
        while(j--){
                if(tmp[j].filters){
                        tmp[j].style.width = tmp[j].style.width || tmp[j].offsetWidth+'px';
                        tmp[j].style.filter = 'alpha(opacity=100)';
                        tmp[j].opaque = tmp[j].filters[0];
                        this.coeff = 1;
                }else{
                        tmp[j].opaque = tmp[j].style;
                }
        }
        return tmp;
}
Fondu.prototype.change = function(sens){
        var prevObj = this.collection[this.courant];
        if(this.encours){
                return false;
        }
        this.encours = true;
        if(sens){
                this.courant++;
                if(this.courant>this.total){
                        this.courant = 0;
                }
        }else{
                this.courant--;
                if(this.courant<0){
                        this.courant = this.total;
                }
        }
        var nextObj = this.collection[this.courant];
        nextObj.style.zIndex = 50;
        var tmpOp = 100;
        var that = this;
        var timer = setInterval(function(){
                if(tmpOp<0){
                        clearInterval(timer);
                        timer = null;
                        prevObj.opaque.opacity = 0;
                        nextObj.style.zIndex = 100;
                        prevObj.style.zIndex = 0;
                        prevObj.opaque.opacity = 100 / that.coeff;
                        that.encours = false;
                }else{
                        prevObj.opaque.opacity = tmpOp / that.coeff;
                        tmpOp -= 1;
                }
        }, 25);
}