SOURCE

<div class="mask"> </div>

@keyframes mask{
		0% {-webkit-mask-position:0px 0px;}
		25% {-webkit-mask-position:619px 0px;}
		50% {-webkit-mask-position:0px 0px;}
		75% {-webkit-mask-position:308px 0px;-webkit-mask-size:100%;}
		100% {-webkit-mask-size:1000%;}
	 }

	.mask{
		width:700px;
		height:392px;
		background:black url("http://img.blog.csdn.net/20170701233330967");
		-webkit-mask-image:url("http://img.blog.csdn.net/20170701233352262");
		animation:mask 5s linear infinite forwards;
	}