效果：

---

---

img{
  border: #000 solid 2px;
  display: block;
  margin: 50px auto;
  /*圆角*/
  border-radius: 50%;
  transition: all 2.0s;
}
img:hover{
  /*旋转*/
  transform: rotate(360deg);
}

<img src="//www.79bk.cn/wp-content/uploads/imageIObf/5cc2be92f26f6.jpg" />