resize 控制大小

#img_box {
  width: 300px;
  resize: both;
  overflow: hidden;
}
#img_box img {
  width: 100%;
  height: 100%;
}

<div id="img_box">
  <img
    src="https://ss0.bdstatic.com/70cFuHSh_Q1YnxGkpoWK1HF6hhy/it/u=1819216937,2118754409&fm=26&gp=0.jpg"
    alt="img"
  />
</div>