var bkimg_obj = null;

var bk_started = false;
var bk_moving = false;
var bk_step = -1;
var bk_timeout = null;
var bk_direction = 1; 
var bk_sequence = 0; //0 = normal, 1 = inverse


function init_page() {
  start_bk_anim();
}

function start_bk_anim() {
  bk_started = true;
  anim_bk();
}

function set_bk_direction(val) {
  bk_direction = val;

  if (!bk_started) {
    bk_started = true;
    anim_bk();
  }

}

function pause_bk_anim() {
  bk_started = false;
}

function resume_bk_anim() {
  bk_started = true;
  anim_bk();
}

function anim_bk() {
  
  if (bk_started) {
    if (bk_step < 7 && bk_direction == 1) {
  
      bk_step++;
      set_bk_src(bk_step);
      if (bk_step == 7) {
        bk_direction = -1;
        if (bk_sequence == 1) {
          bk_sequence = 0;
        } else {
          bk_sequence = 1;
        }
      }
      if (bk_step == 0 && bk_moving) {
        anim_bk();
      } else {
        bk_moving = true ;
        bk_timeout = setTimeout("anim_bk();", 1000);
      }
  
    } else {
  
      bk_step--;
  
      if (bk_step == -1) {
        
        bk_direction = 1;
        bk_step = -1;
        anim_bk();
      } else {
        set_bk_src(bk_step);
        bk_moving = true;
        bk_timeout = setTimeout("anim_bk();", 1000);
      }
  
    }
  }

}

function set_bk_src(step) {
  var obj = document.getElementById("bk_img");

  if (bk_sequence == 0) {
    obj.src = "images/index/bk" + step + ".jpg";
  } else {
    obj.src = "images/index/bk" + step + "_.jpg";
  }
  

}