window.fullScreen = false;

function zoom(id) {
    if (window.fullScreen == false) {
        var img = document.getElementById(id);
        img.style.width = "95%";
        img.style.height = "auto";
        img.style.position = "fixed";
        img.style.top = "0px";
        window.fullScreen = true;
    }
    else {
        var img = document.getElementById(id);
        img.style.width = "70%";
        img.style.height = "auto";
        img.style.position = "relative";
        window.fullScreen = false;
    }
}