Centre an img within a div

HTML

<html>
    <body>
        <div>
            <img src="http://www.waleoyediran.com/wp-content/uploads/2011/04/stackoverflow.png"/>                
        </div>
    </body>    
</html>

CSS

div, img {
 border: 1px solid black;  
}

div {
  width: 200px;
  height: 200px;
  text-align: center;
  line-height: 200px;
}

img {
  max-width: 190px;
  max-height: 190px;
  vertical-align: middle;    
}