使一张图片沾满整个屏幕且不带滚动条
效果图：
代码：
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta content="width=device-width, height=device-height,initial-scale=1.0, minimum-scale=1.0, maximum-scale=1.0, user-scalable=no"
name="viewport">
<title>测试页面</title>
</head>
<body>
<div class="content no-msg top">
<img class="back" src="../assets/images/back.jpeg" alt="">
<img class="scan" src="../assets/images/scan.png" alt="">
</div>
</body>
<style>
html,body {
margin:0;
padding:0;
overflow: hidden;
}
.no-msg{
width: 100%;
height: 100%;
top:0;
z-index: 1;
position: absolute;
}
.no-msg .back {
display: block;
outline: none;
border:0;
height: 100%;
width: 100%;
}
.scan{
z-index: 1000000000;
position: absolute;
top: 40%;
left: 33%;
width: 34%;
/* height: 20%; */
}
</style>
</html>
