function image_resize( img, width_size, height_size ) {
  var now_width  = img.width
  var now_height = img.height
  var rate;

  if(now_width < now_height) {
    img.height = height_size;
    rate = now_width / now_height;
    img.width = parseInt (height_size * rate);
//    img.style.position = "relative";
//    img.style.left = (width_size - img.width) / 2 + "px";	
  }
  else if (now_width > now_height) {
    img.width = width_size;
    rate = now_height / now_width;
    img.height = parseInt (width_size * rate);
    img.style.position = "relative";
    img.style.top = (height_size - img.height) / 2 + "px";
  } else {
    img.width = width_size;
    img.height = height_size;
  }
}