CSS中背景图片透明度问题小结
.demo1{
width: 500px;
height: 300px;
line-height: 50px;
text-align: center;
}
.demo1:before{
background: url(http://csssecrets.io/images/tiger.jpg) no-repeat;
background-size: cover;
width: 500px;
height: 300px;
content: "";
position: absolute;
top: 0;
left: 0;
z-index: -1;/*-1 可以当背景*/
-webkit-filter: blur(3px);
filter: blur(3px);
}