.img {display:block;position:relative;width:800px;height:450px;margin:0auto;}
.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,lefttop,righttop, 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:left1s ease0s; }
<-html->
<a><img http://img.loveqiao.com/pic1.jpg"width="800"></a>
