var clock = 30;
var reset = clock;
var timer = setTimeout("refresh(clock)", 1000);

function refresh(ticks){
    clock = ticks - 1;
    document.getElementById('refresh').innerHTML = clock;
    
    if (clock) {
        timer = setTimeout("refresh(clock)", 1000);
    }
    else {
        window.location.reload();
    }
}

function imgviewer(file, reset){
    document.getElementById('viewer').src = file;
    
    if (reset) {
        clearTimeout(timer);
        setTimeout("refresh(reset)", 1000);
    }
}