html - Text vertically and horizontally centered over a responsive image

Question

I'm looking to center text both vertically and horizontally over an image that grows when the page gets wider.

I originally had the image set as the background for a div of fixed height, in which case it was relatively easy to center it, but because background images aren't structural, I couldn't set the height to be an automatic function of the width, and I had to toss this option out when I went for a more responsive design.

So I've currently got a div with two elements in it, img and overlay text. The image width is set to 100% of the width of its container, and the height varies accordingly. As a consequence, though, I can't set the overlay text to be postion:absolute and top:80px or something, because the distance from the top will have to vary. And even doing top:25% or whatever doesn't work, because a) if that page width shrinks to squeeze the text, or if there's just more text, the vertical centering is thrown off when there are more/less lines, and b) the percentage is arbitrary -- it's not 50 or something, because that would put the top of the text overlay 50% down the image, when I want the center of the overlay to be there.

I've looked, among other things, at this post, which is definitely close -- but in both solutions, the image height is incapable of resizing, and in the former, the JS loads at page load, but then freezes, so that if I change page width/height, things get out of whack. Ideally, this solution wouldn't involve JS for just that reason (even if it reloaded on every resize, that feels non-ideal), but if that's the only solution, I'll take it.

Also, just for added details/fun, I've set a max-height on the image, because I don't want it to exceed roughly 300px height, even on a cinema display.

Basic fiddle of current attempt here, and identical code below. Any ideas? Thanks!

html

<div class='quotation_div'>
  <img src='http://www.mountainprofessor.com/images/mount-ranier-mount-features-2.jpg'>
  <div class='overlay'>
      <p>Any reasonable amount of text should be able to go here. I want it to be able to center vertically even if it takes up 2 or 3 lines.</p>
  </div>
</div>

css

.quotation_div {
position: relative;
display: table;
}
img {
   width: 100%;
   max-height: 300px;
}
.overlay {
    z-index: 99;
    width: 70%;
    margin-left: 15%;
    vertical-align: middle;
    position: absolute;
    top: 25%; /* Obvious problem, cause it's arbitrary */
}
p {
    text-align: center;
    color: red;
    font-size: 165%;
    font-weight: lighter;
    line-height: 2;
}

Answer 1

You can use CSS background-size to set the width to 100% and the height will be calculated to maintain aspect ratio.

Here's a fiddle using that technique.

If you want the image as an HTML element then I suggest you set it's position to absolute and use the same method of disply:table-cell to center the overlay:

Here's a fiddle using that method, this one stretches the image because of the max-height.