.img {
display:block;
position: relative;
width:800px;
height:450px;
margin:0 auto;
}
.img:before {
content: "";
position: absolute;
width:200px;
height: 100%;
top: 0;
left: -150px;
overflow: hidden;
background: -moz-linear-gradient(left, rgba(255,255,255,0)0, rgba(255,255,255,.2)50%, rgba(255,255,255,0)100%);
background: -webkit-gradient(linear, left top, right top, color- stop(0%, rgba(255,255,255,0)), color-stop(50%, rgba(255,255,255,.2)), color-stop(100%, rgba(255,255,255,0)));
background: -webkit-linear-gradient(left, rgba(255,255,255,0)0, rgba(255,255,255,.2)50%, rgba(255,255,255,0)100%);
background: -o-linear-gradient(left, rgba(255,255,255,0)0, rgba(255,255,255,.2)50%, rgba(255,255,255,0)100%);
-webkit-transform: skewX(-25deg);
-moz-transform: skewX(-25deg)
}
.img:hover:before {
left: 150%;
transition: left 1s ease 0s;
}