<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport"
content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
<style>
body{
/*background-image:url(./timg.jpg);*/
}
#mm{
background-image:url(./b.jpg);
width:100%;height:100%;
/*关键：否则位置不是中心*/
background-position: center;
/*关键：把背景图像扩展至足够大，以使背景图像完全覆盖背景区域。*/
background-size: cover;
background-repeat: no-repeat;
}
</style>
</head>
<body>
<div style="width:200px;height:180px;">
<div id="mm" style=""></div>
</div>
</body>
</html>
图片.png
图片.png
效果：
图片.png
图片.png
