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

  if(now_width*3 < now_height*4){
    img.height = height_size;
    img.style.position = "relative";
  }
  else if (now_width*3 >= now_height*4) {
    img.width  = width_size;
    img.style.position = "relative";
   }

}