SOURCE

<div class="over-img">
    <div class="img1"></div>
    <div class="light"></div>
</div>

.over-img{
    width: 200px;
    height: 200px;
    position: relative;
    overflow: hidden;
}
.img1{
    width: 100%;
    height: 100%;
    background: #000;
}
.light{
    cursor: pointer;
    position: absolute;
    display: block;
    width: 30px;
    height: 100%;
    top: 0;
    left: -100px;
    z-index: 10;
    pointer-events: none;
    transform: skewX(-25deg);
    transition: left 3s;
    background-image:linear-gradient(to right,rgba(255,255,255,0) 0,rgba(255,255,255,0.5) 50%,rgba(255,255,255,0) 100%);
}
.over-img:hover .light{
    left: 400px;
}