Centering images vertically

HTML:

<ul>
  <li><img src="image1.png" /></li>
  <li><img src="image2.png" /></li>开发者_开发问答;
  <li><img src="image3.png" /></li>
  <li><img src="image4.png" /></li>
  <li><img src="image5.png" /></li>
  <li><img src="image6.png" /></li>
</ul>

... the images are all different sizes, I'd like to center them vertically.

jQuery:

$('ul li').css('paddingTop', height($("ul li").height() - ("li img") / (2)));
# padding-top = height of li - height of image / 2

.. but this isn't working.

A Better Way?

If you're using jQuery, why not use one of the centering plugins?

// make sure li in this case is position:relative;
$("ul li img").center();

Present Problems

The following line has many problems:

height($("ul li").height() - ("li img") / (2))

height() is not a function, unless you've declared it elsewhere. If so, what is it suppose to do exactly? Note, I'm not referring to $.height(), which is a valid method in the jQuery Framework. Additionally, ("li img") is not a numerical value, so dividing it by 2 makes no sense.

Perhaps the following may be more helpful:

$("ul li img").each(function(){
  var pHeight = $(this).parent().height();
  var iHeight = $(this).height();
  var diff    = Math.round(pHeight - iHeight);
  $(this).parent().css("paddingTop", diff);
});

I think @Jonathan's answer is what you should follow ( centering plugin ) but here is your code cleaned up quite a bit:

$('ul li').each(function(){
   var $li = $(this), $img = $li.find('img');
   $img.css('padding-top', ($li.height() / 2) - ($img.height() / 2));
});

Of course, this will only work when the li has a fixed height in the CSS.

Vertically center

$('ul li img').each(function(){
  var height=$(this).outerHeight(),
  li=$(this).closest('li'),
  li_height=li.outerHeight();
  li.height(li_height+'px');
  $(this).css({marginTop: (li_height-height)/2+'px'});
});