JSFiddle - React, Tailwind, and code Playground

HTML

<div><span></span></div>

CSS

div {
    background-image: url(http://im.tech2.in.com/gallery/2012/dec/stockimage_070930177527_640x360.jpg);
    height: 400px;
    width: 400px;
}

div span {
    display: block;
    height: 100%;
    width: 100%;
    opacity: 0;
    background: rgba(0,0,0,.5);
    -moz-transition: all 1s;
    -webkit-transition: all 1s;
    transition: all 1s;
}

div:hover span {
    opacity: 1;
}