Vertically align an image inside a div with responsive height

SO #18516317 http://stackoverflow.com/questions/18516317/vertically-align-an-image-inside-a-div-with-responsive-height/18516474#18516474

by SpiceLab

HTML

<div class="responsive-container">
    <div class="dummy"></div>
    <div class="img-container">
        <img src="http://placehold.it/150x150" alt="" />
    </div>
</div>

CSS

.responsive-container {
    position: relative;
    width: 100%;
    border: 1px solid black;
}

.dummy {
    padding-top: 100%; /* forces 1:1 aspect ratio */
}

.img-container {
    position: absolute;
    top: 0;
    bottom: 0;
    left: 0;
    right: 0;

    text-align:center; /* Align center inline elements */
    font: 0/0 a;
}

.img-container:before {
    content: ' ';
    display: inline-block;
    vertical-align: middle;
    height: 100%;
}

.img-container img {
    vertical-align: middle;
    display: inline-block;
}