<!DOCTYPE html>
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width,initial-scale=1,
minimum-scale=1,maximum-scale=1,user-scalable=no" />
<title></title>
<style>
.box{
position: relative;
width: 100%;
height: 0;
padding-top: 70%;
transform-origin: top;
background-image:url(img/banner.jpg);
background-repeat: no-repeat;
background-size: cover;
}
.filter{
position: absolute;
top: 0;
left: 0;
width: 100%;
height: 100%;
background: rgba(7, 17, 27, 0.4);
}
</style>
</head>
<body>
<div class="box">
<div class="filter"><!--蒙层--></div>
</div>
</body>
</html>