function img_popup(url, width, height) {
    var winl = (screen.width - width)/2;
    var wint = (screen.height - height)/2;
    window.open(url, '', 'toolbar=0, location=0, menubar=0, scrollbars=0, resizable=0, width=' + width + ', height=' + height + ', top=' + wint + ', left=' + winl + '')
}