不定宽高div内图片垂直居中的css样式

div{
display: table-cell;
}

<div><span></span><img src="test.png" alt=""></div>

div{
width: 100px;
height: 100px;
border: 1px solid #c;
}
span{
line-height: 100%;
vertical-align: middle;
display: inline-block;
height: 100%;
}
img{
width: 100%;
vertical-align: middle;
}