边框0.5px的实现方法

原理: css3 的缩放   ---->    transform: scale()

　　完整代码如下：

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style>
        div {
            height: 200px;
            width: 200px;
            margin: 50px auto;
            position: relative;
            /*background: #f4f4f4;*/
        }
        .box::after {
            content: ‘‘;
            position: absolute;
            left: 0;
            top: 0;
            z-index:-1;
            width: 200%;
            height:200%;
            border:1px solid #000000;
            -webkit-transform-origin: 0 0;
            transform-origin: 0 0;
            -webkit-transform: scale(.5, .5);
            transform: scale(.5, .5);
            -webkit-transform: scale(.5, .5);
            -ms-transform: scale(.5, .5);
            z-index: 1;   /*不加的话，在有背景的情况下就只有下右两边框*/
        }
        .bd-t::after {
            content: "";
            position: absolute;
            top: 0;
            left: 0;
            width: 100%;
            border-top: 1px solid #000;
            transform: scaleY(.5);
            -webkit-transform: scaleY(.5);
            -ms-transform: scaleY(.5);
        }
        .bd-l::after {
            content: "";
            position: absolute;
            top: 0;
            left: 0;
            height: 100%;
            border-left: 1px solid #000;
            transform: scaleX(.5);
            -webkit-transform: scaleX(.5);
            -ms-transform: scaleX(.5);
        }
        .box1 {
            height: 200px;
            width: 200px;
            margin: 50px auto;
            position: relative;
            border: 1px solid #000;
            /*background: #09f;*/
        }
    </style>
</head>
<body>
    <div class="box">
        四条边框0.5px
    </div>
    <div class="bd-t">
        顶部边框0.5px
    </div>
    <div class="bd-l">
        左边框0.5px
    </div>
    <div class="box1">参考相</div>

</body>
</html>