Styling image along with caption, if it exists, in Wordpress - css

Question

This is Wordpress-related question, but since desired solution is purely CSS-related, I posted it in here, not at wordpress.stackexchange.com.
In my current style, if image has no following caption, it is placed using HTML code like that:
<p>
<a href="http://cnn.com/file.jpg">
<img src="http://cnn.com/file-300x225.jpg" alt="" width="300" height="225" class="aligncenter size-medium wp-image-55">
</a>
</p>
In my current style, it is styled like that:
img {
display: block;
padding: 5px;
background-color: #eee;
border: 1px solid #ddd;
}
Which draws simple border around it.
If there is a caption following image, entire HTML in this part is a little bit more complex:
<div id="attachment_55" class="wp-caption aligncenter" style="width: 310px">
<a href="http://cnn.com/file.jpg">
<img src="http://cnn.com/file-300x225.jpg" alt="" width="300" height="225" class="size-medium wp-image-55">
</a>
<p class="wp-caption-text">Caption</p>
</div>
Currently caption is not styled at all (as per my currently selected theme).
What I would like to achieve is to have entire div styled (image and caption), if there is any caption. If I'm not mistaken, that would require to style img (as currently) only, if it is not followed by <p class="wp-caption-text">. If it is, then img should not be styled at all and it second-in-row parent (<div class="wp-caption">) should be styled instead.
That's all for the algorithm. But how to code this in CSS (and whether it is possible at all) -- I don't know.
The simpliest solution would be to never style img and always style <div class="wp-caption"> instead, no matter if there is caption following image or not. But the problem is, that Wordpress is adding that div only, if there is a caption. So styling only it, would result in no border at all, if there is only image.

Answer 1

if you can use Jquery.
you can manipulate the markup then. if the pattern of your img and img with caption is going to be like that, you can do this.
$('img').each(function(){
if($(this).parent().parent().hasClass("wp-caption")){
$(this).parent().parent().addClass('img');
}
});
am sure this code can be optimized even better, but it should give you an idea.
see this fiddle