var BANNER_IMAGES = ['banner2.jpg', 'banner5.png', 'vball-jchung.jpg', 'banner4.png'];
var CUR_BANNER = 0;

function show_next_or_prev_banner(incre) {
  CUR_BANNER = (CUR_BANNER+incre)%(BANNER_IMAGES.length);  
  $('#banner-pic').attr('src', IMAGE_PATH + "banners/" + BANNER_IMAGES[CUR_BANNER]);
  $('#banner-pic').animate( {opacity: 1}, 500);
}

function next_banner() {
  $('#banner-pic').animate(
    {opacity: 0}, 500, function() {
      show_next_or_prev_banner(1);
    });
}

function prev_banner() {
  $('#banner-pic').animate(
    {opacity: 0}, 500, function() {
      show_next_or_prev_banner(BANNER_IMAGES.length-1);
    });
}

function init_banner() {
  $('#banner-pic').attr('src', IMAGE_PATH + "banners/" + BANNER_IMAGES[0]);
  setInterval(next_banner, 15000);
}