Does :before not work on img elements?

I'm trying to use the :before selector to place an image over another image, but I'm finding that it simply doesn't work to place an image before an img element, only some other element. Specifically, my styles are:

.container
{
   position: relative;
   display: block;
}

.overlay:before
{
    content: url(images/[someimage].png);
    position: absolute;
    left:-20px;
    top: -20px;
}

and I find that this works fine:

<a href="[url]" class="container">
  <span class="overlay"/>
  <img width="200" src="[url]"/>
</a>

but this does not:

<a href="[url]" class="container">
  <img width="200" src="[url]" class="overlay"/>
</a>

I can use a div or p element instead of that span, and the browser correctly overlays my image over the image in the img element, but if I apply the overlay class to the img itself, it doesn't work.

I'd like to get this working because that extra span offends me, but more importantly, I've got about 100 blog posts that I'd like to modify, and I can do this in one go if I could just modify the stylesheet, but if I have to go back and add an extra span element in between the a and img elements, this will be a lot more work.

Solution 1:

Unfortunately, most browsers do not support using :after or :before on img tags.

http://lildude.co.uk/after-css-property-for-img-tag

However, it IS possible for you to accomplish what you need with JavaScript/jQuery. Check out this fiddle:

http://jsfiddle.net/xixonia/ahnGT/

$(function() {

    $('.target').after('<img src="..." />');

});

Edit:

For the reason why this isn't supported, check out coreyward's answer.

Solution 2:

The before and after pseudo-selectors don't insert HTML elements — they insert text before or after the existing content of the targeted element. Because image elements don't contain text or have descendants, neither img:before or img:after will do you any good. This is also the case for elements like <br> and <hr> for the same reason.

Solution 3:

I found a way to make this work in pure css:

The I'm just fake content-method

a pure CSS method to enable img:after.

You can check out the CodePen: I'm just fake content or see the source.

Source & Snippet

img {
    /* hide the default image */
    height:0;
    width:0;

    /* hide fake content */
    font-size:0;
    color:transparent;

    /* enable absolute position for pseudo elements */
    position:relative;

    /* and this is just fake content */
    content:"I'm just fake content";
}

/* initial absolute position */
img:before,
img:after {
    position:absolute;
    top:0;
    left:0;    
}

/* img:before - chrome & others */
img:before {
    content:url(http://placekitten.com/g/250/250);
}

/* img:before - firefox */
body:not(:-moz-handler-blocked) img:before {
    padding:125px;
    background:url(http://placekitten.com/g/250/250) no-repeat;
}

/* img:after */
img:after {
    /* width of img:before */
    left:250px;

    content:url(http://lorempixel.com/350/200/city/1);
}

<img
    alt="You are watching the ~ I'm just fake content ~ method"  
/>

Browser support

✓ Chrome 10+

✓ Firefox 11+

✓ Opera 9.8+

✓ Safari

No support

⊗ Internet Explorer 8 / 9

Please test in other browsers

Solution 4:

Due to the nature of <img> being a replaced element, document styling doesn’t affected it.

To reference it anyway, <picture> provides an ideal, native wrapper that can have pseudo-elements attached to it, like so:

img::after,
picture::after{
    content:"\1F63B";
    font-size:larger;
    margin:-1em;
}

<img src="//placekitten.com/110/80">

<picture>
    <img src="//placekitten.com/110/80">
</picture>