function GetID(id) { return document.getElementById(id); } 
function montrerFenetre(src, div, img) {
    var overlay = GetID('overlay');
    overlay.style.visibility = "visible";

	var my_image = GetID(img);
	my_image.src = src;
	
	var my_window = GetID(div);
	my_window.style.visibility = "visible";
}

function cacherFenetre(div) {
    var overlay = GetID('overlay');
    overlay.style.visibility = "hidden";

	var my_window = GetID(div);
	my_window.style.visibility = "hidden";
}