<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<style>
img {
border: #000 solid 5px;
display: block;
margin: 50px auto;
border-radius: 50%;
border-top-color:#fff;
border-right-color:red;
border-bottom-color:green;
transition: all 1.5s;
}
img:hover {
transform: rotate(90deg);
}
</style>
</head>
<body>
<img src="images/assets/5.jpg" />
</body>
</html>
原文：http://www.cnblogs.com/123lucy/p/6682483.html