css如何实现图片在div中垂直居中

div{

        width:200px;

        height: 200px;

        margin:300px auto;

        display: table-cell;//作为一个表格单元格显示

        vertical-align: middle;//设置垂直对齐方式

        text-align: center;//设置水平对其方式

        border:1px solid #ccc;

    }

     img {

        width:80px;

        height:50px;

    }

div{

    width:200px;

    height:200px;

    border: 1px solid #ccc;

    position: relative;

}

img{

    position: absolute;

    width:80px;

    height: 50px;

    top:50%;

    left:50%;

    margin-top: -40px;//向上40px

    margin-left: -25px;//向左25px

}