巧用CSS3 border制作图片遮罩效果 

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 
<html xmlns="http://www.w3.org/1999/xhtml"> 
<head> 
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 
<title>无标题文档</title> 
<style type="text/css">
.trans {
-webkit-transition: 0.3s ease;
-moz-transition: 0.3s ease;
-ms-transition: 0.3s ease;
-o-transition: 0.3s ease;
transition: 0.3s ease;
}
.test_outer {
display: block;
width: 200px;
height: 200px;
margin: 1em auto;
position: relative;
overflow: hidden;
}
.test_cover {
width: 40px;
height: 40px;
border: 200px solid rgba(0, 0, 0, .35);
border-radius: 50%;
position: absolute;
left: -115px;
top: -165px;
}
.test_cover:hover {
width: 140px;
height: 140px;
left: -170px;
top: -165px;
}
.test_cover:hover:after {
content: "秋思-一叶知秋！";
text-align:center;
margin:55px 0 0 12px;
color: #fff;
font: bold 16px/1.2 '微软雅黑';
text-shadow: 1px 1px rgba(0, 0, 0, .35);
position: absolute;
}
</style> 
</head> 

<body> 

<a href="#" class="test_outer"> 
<span class="test_cover trans"></span> 
<img src="http://center.w3cfuns.com/data/avatar/000/00/64/47_avatar_middle.jpg" width="200" height="200" /> 
</a> 
</body> 
</html>

其实现原理是利用个border偌大的半透明边框属性（demo中边框宽度200像素），边框颜色为rgba黑色半透明，然后50%圆角。再用用定位把它覆盖在图片上面。
主要核心代码:

.test_cover {
width: 40px;
height: 40px;
border: 200px solid rgba(0, 0, 0, .35);
border-radius: 50%;
position: absolute;
left: -115px;
top: -165px;
}

然后外面再用个父容器把它溢出隐藏掉就可以了

.test_outer {
display: block;
width: 200px;
height: 200px;
margin: 1em auto;
position: relative;
overflow: hidden;
}

就这么简单....






posted @ 2012-04-07 09:44  脉凌网络  阅读(930)  评论(0)  编辑  收藏  举报