工作中发现，有些div的背景图是小图，F12查看其实是一整张大图。实现方法是通过background-position属性来实现的，CSS代码如下：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
</head>
<style>
.div-outer {
width: 100px;
height: 100px;
border: 1px solid gray;
}
.div-inner {
margin-left: 50%;
border: 1px solid red;
background: url("./resources/pa.png");
/*div的宽高=子图的宽高、背景图的起始位置=子图的起始位置距离大图左上角的距离取负数。参见：https://www.cnblogs.com/iyangyuan/archive/2013/06/01/3111704.html*/
background-position: -61px -41px;
width: 43px;
height: 37px;
}
</style>
<body>
<div class="div-outer">
<div class="div-inner"></div>
</div>
</body>
</html>
