.item-img {
    padding-bottom: 56.25%;
    position: relative;
    display: block;
    height: 0;
    overflow: hidden;
    background: #222;
}
.item-img img {
    position: absolute;
    top: 0;
    bottom: 0;
    left: 0;
    width: 100%;
    height: 100%;
    border: 0;
}