var image1 = new Image();
image1.src = "img/menu/groupe.jpg";
var image2 = new Image();
image2.src = "img/menu/tourisme-durable.jpg";
var image3 = new Image();
image3.src = "img/menu/notre-stage.jpg";
var image4 = new Image();
image4.src = "img/menu/commerce-equitable.jpg";

function roll(img_name, img_src) {
    document[img_name].src = img_src;
}