css3实现背景模糊的三种方式

一、普通背景模糊

代码:

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<head>
<Style>
html,
body {
width: 100%;
height: 100%;
}

* {
margin: 0;
padding: 0;
}

/*背景模糊*/
.bg {
width: 100%;
height: 100%;
position: relative;
background: url("./bg.jpg") no-repeat fixed;
background-size: cover;
box-sizing: border-box;
filter: blur(2px);
z-index: 1;
}

.content {
position: absolute;
left: 50%;
top: 50%;
transform: translate(-50%, -50%);
width: 200px;
height: 200px;
text-align: center;
z-index: 2;
}
</Style>
</head>

<body>
<div class="bg">
<div class="content">背景模糊</div>
</div>
</body>

效果如下所示:

这样写会使整个div的后代模糊并且还会出现白边,导致页面非常不美观,要想解决这个问题,我们可以使用伪元素,因为伪元素的模糊度不会被父元素的子代继承。

代码:

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<head>
<Style>
html,
body {
width: 100%;
height: 100%;
}

* {
margin: 0;
padding: 0;
}

/*背景模糊*/
.bg {
width: 100%;
height: 100%;
position: relative;
background: url("./bg.jpg") no-repeat fixed;
background-size: cover;
box-sizing: border-box;
z-index: 1;
}

.bg:after {
content: "";
width: 100%;
height: 100%;
position: absolute;
left: 0;
top: 0;
/* 从父元素继承 background 属性的设置 */
background: inherit;
filter: blur(2px);
z-index: 2;
}


.content {
position: absolute;
left: 50%;
top: 50%;
transform: translate(-50%, -50%);
width: 200px;
height: 200px;
text-align: center;
z-index: 3;
}
</Style>
</head>

<body>
<div class="bg">
<div class="content">背景模糊</div>
</div>
</body>

效果如下所示:

二、背景局部模糊

上一个效果会了之后,局部模糊效果就比较简单了。

代码:

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<head>
<Style>
html,
body {
width: 100%;
height: 100%;
}

* {
margin: 0;
padding: 0;
}

/*背景模糊*/
.bg {
width: 100%;
height: 100%;
position: relative;
background: url("./bg.jpg") no-repeat fixed;
background-size: cover;
box-sizing: border-box;
z-index: 1;
}

.content {
position: absolute;
left: 50%;
top: 50%;
transform: translate(-50%, -50%);
width: 200px;
height: 200px;
background: inherit;
z-index: 2;
}

.content:after {
content: "";
width: 100%;
height: 100%;
position: absolute;
left: 0;
top: 0;
background: inherit;
filter: blur(15px);
/*为了模糊更明显,调高模糊度*/
z-index: 3;
}

.content>div {
width: 100%;
height: 100%;
text-align: center;
line-height: 200px;
position: absolute;
left: 0;
top: 0;
z-index: 4;
}
</Style>
</head>

<body>
<div class="bg">
<div class="content">
<div>背景局部模糊</div>
</div>
</div>
</body>

效果如下图所示:

三、背景局部清晰

代码:

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<head>
<Style>
html,
body {
width: 100%;
height: 100%;
}

* {
margin: 0;
padding: 0;
}

/*背景模糊*/
.bg {
width: 100%;
height: 100%;
position: relative;
background: url("./bg.jpg") no-repeat fixed;
background-size: cover;
box-sizing: border-box;
z-index: 1;
}

.bg:after {
content: "";
width: 100%;
height: 100%;
position: absolute;
left: 0;
top: 0;
background: inherit;
filter: blur(5px);
z-index: 2;
}

.content {
position: absolute;
left: 50%;
top: 50%;
transform: translate(-50%, -50%);
width: 200px;
line-height: 200px;
text-align: center;
background: inherit;
z-index: 3;
box-shadow: 0 0 10px 6px rgba(0, 0, 0, .5);
}
</Style>
</head>

<body>
<div class="bg">
<div class="content">
<div>背景局部清晰</div>
</div>
</div>
</body>

效果如下图所示: