html中给图片添加遮罩阴影效果

<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title>DYH</title>
		<style type="text/css">
			.item{
				position: relative;
				width: 300px;
				height: 300px;
				margin: 50px auto;
				border-radius: 50%;
				overflow: hidden;
				border: 2px solid #fff;
				box-shadow: 0 0 5px #333;
			}
			.item img{
				width: 300px;
				height: 300px;
			}
			.cover{
				width: 300px;
				height: 300px;
				background-color: rgba(0,0,0,0.3);
				position: absolute;
				top: 0;
				left: 0;
				color: #fff;
				text-align: center;
				line-height: 300px;
				font-size: 30px;
				border-radius: 50%;
			}
			
			.item01 .cover{
				transform: rotate(90deg);
				transform-origin: right bottom;
				transition: transform 2s;
			}
			.item01:hover .cover{
				transform: rotate(0deg);
			}
			
			.item02 .cover{
				opacity: 0;
				transition: opacity 2s;
			}
			.item02:hover .cover{
				opacity: 1;
			}
			
			.item03 .cover{
				transform: translate(-300px);
				transition: transform 2s;
			}
			.item03:hover .cover{
				transform: translate(0px);
			}
			
			.item04 .cover{
				transform: scale(0);
				transition: transform 2s;
			}
			.item04:hover .cover{
				transform: scale(1,1);
			}
			
		</style>
	</head>
	<body>
		<div class="item item01">
			<img src="img/img02.jpg" >
			<div class="cover">cover</div>
		</div>
		<div class="item item02">
			<img src="img/img02.jpg" >
			<div class="cover">cover</div>
		</div>
		<div class="item item03">
			<img src="img/img02.jpg" >
			<div class="cover">cover</div>
		</div>
		<div class="item item04">
			<img src="img/img02.jpg" >
			<div class="cover">cover</div>
		</div>
	</body>
</html>