日常css技巧小结（1）--背景透明度改变对内容无影响-HTML Tutorial-php.cn

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日常css技巧小结（1）--背景透明度改变对内容无影响

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Jun 01, 2016 pm 02:32 PM

刚开始出现的错误，内容会受到背景透明度改变的影响：如图：

代码：

<span style="color: #0000ff;"><span style="color: #ff00ff;">DOCTYPE html</span><span style="color: #0000ff;">></span>
<span style="color: #0000ff;"><span style="color: #800000;">html </span><span style="color: #ff0000;">lang</span><span style="color: #0000ff;">="en"</span><span style="color: #0000ff;">></span>
<span style="color: #0000ff;"><span style="color: #800000;">head</span><span style="color: #0000ff;">></span>
    <span style="color: #0000ff;"><span style="color: #800000;">meta </span><span style="color: #ff0000;">charset</span><span style="color: #0000ff;">="UTF-8"</span><span style="color: #0000ff;">></span>
    <span style="color: #0000ff;"><span style="color: #800000;">title</span><span style="color: #0000ff;">></span>Document<span style="color: #0000ff;"></span><span style="color: #800000;">title</span><span style="color: #0000ff;">></span>
    <span style="color: #0000ff;"><span style="color: #800000;">style</span><span style="color: #0000ff;">></span><span style="background-color: #f5f5f5; color: #800000;">
        div</span><span style="background-color: #f5f5f5; color: #000000;">{</span><span style="background-color: #f5f5f5; color: #ff0000;">
            width</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;">300px</span><span style="background-color: #f5f5f5; color: #000000;">;</span><span style="background-color: #f5f5f5; color: #ff0000;">
            height</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 300px</span><span style="background-color: #f5f5f5; color: #000000;">;</span><span style="background-color: #f5f5f5; color: #ff0000;">
            margin</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 50px auto</span><span style="background-color: #f5f5f5; color: #000000;">;</span><span style="background-color: #f5f5f5; color: #ff0000;">
            line-height</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 300px</span><span style="background-color: #f5f5f5; color: #000000;">;</span><span style="background-color: #f5f5f5; color: #ff0000;">
            text-align</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> center</span><span style="background-color: #f5f5f5; color: #000000;">;</span><span style="background-color: #f5f5f5; color: #ff0000;">
            background</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> red</span><span style="background-color: #f5f5f5; color: #000000;">;</span><span style="background-color: #f5f5f5; color: #ff0000;">
            color</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> #000</span><span style="background-color: #f5f5f5; color: #000000;">;</span><span style="background-color: #f5f5f5; color: #ff0000;">
            font-size</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 30px</span><span style="background-color: #f5f5f5; color: #000000;">;</span><span style="background-color: #f5f5f5; color: #ff0000;">
            -webkit-opacity</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 0.2</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
        <span style="background-color: #f5f5f5; color: #000000;">}</span>
    <span style="color: #0000ff;"></span><span style="color: #800000;">style</span><span style="color: #0000ff;">></span>
<span style="color: #0000ff;"></span><span style="color: #800000;">head</span><span style="color: #0000ff;">></span>
<span style="color: #0000ff;"><span style="color: #800000;">body</span><span style="color: #0000ff;">></span>
    <span style="color: #0000ff;"><span style="color: #800000;">div class=“wrap”</span><span style="color: #0000ff;">></span><span style="color: #000000;">
        我爱夏天
    </span><span style="color: #0000ff;"></span><span style="color: #800000;">div</span><span style="color: #0000ff;">></span>
<span style="color: #0000ff;"></span><span style="color: #800000;">body</span><span style="color: #0000ff;">></span>
<span style="color: #0000ff;"></span><span style="color: #800000;">html</span><span style="color: #0000ff;">></span></span></span></span></span></span></span></span></span>

解决方法一：

在div.wrap内再加一个div。作为蒙版，对其设置透明度的变化样式，并且让内容相对于wrap绝对定位，要记得给wrap设置相对定位！！

<span style="color: #0000ff;"><span style="color: #ff00ff;">DOCTYPE html</span><span style="color: #0000ff;">></span>
<span style="color: #0000ff;"><span style="color: #800000;">html </span><span style="color: #ff0000;">lang</span><span style="color: #0000ff;">="en"</span><span style="color: #0000ff;">></span>
<span style="color: #0000ff;"><span style="color: #800000;">head</span><span style="color: #0000ff;">></span>
    <span style="color: #0000ff;"><span style="color: #800000;">meta </span><span style="color: #ff0000;">charset</span><span style="color: #0000ff;">="UTF-8"</span><span style="color: #0000ff;">></span>
    <span style="color: #0000ff;"><span style="color: #800000;">title</span><span style="color: #0000ff;">></span>Document<span style="color: #0000ff;"></span><span style="color: #800000;">title</span><span style="color: #0000ff;">></span>
    <span style="color: #0000ff;"><span style="color: #800000;">style</span><span style="color: #0000ff;">></span><span style="background-color: #f5f5f5; color: #800000;">
        .wrap</span><span style="background-color: #f5f5f5; color: #000000;">{</span><span style="background-color: #f5f5f5; color: #ff0000;">
            width</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;">300px</span><span style="background-color: #f5f5f5; color: #000000;">;</span><span style="background-color: #f5f5f5; color: #ff0000;">
            height</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 300px</span><span style="background-color: #f5f5f5; color: #000000;">;</span><span style="background-color: #f5f5f5; color: #ff0000;">
            margin</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 50px auto</span><span style="background-color: #f5f5f5; color: #000000;">;</span><span style="background-color: #f5f5f5; color: #ff0000;">    
            position</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> relative</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
        <span style="background-color: #f5f5f5; color: #000000;">}</span><span style="background-color: #f5f5f5; color: #800000;">
        .con</span><span style="background-color: #f5f5f5; color: #000000;">{</span><span style="background-color: #f5f5f5; color: #ff0000;">
            width</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 300px</span><span style="background-color: #f5f5f5; color: #000000;">;</span><span style="background-color: #f5f5f5; color: #ff0000;">
            height</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 300px</span><span style="background-color: #f5f5f5; color: #000000;">;</span><span style="background-color: #f5f5f5; color: #ff0000;">
            background</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> red</span><span style="background-color: #f5f5f5; color: #000000;">;</span><span style="background-color: #f5f5f5; color: #ff0000;">
            -webkit-opacity</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 0.2</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
        <span style="background-color: #f5f5f5; color: #000000;">}</span><span style="background-color: #f5f5f5; color: #800000;">
        span</span><span style="background-color: #f5f5f5; color: #000000;">{</span><span style="background-color: #f5f5f5; color: #ff0000;">
            position</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> absolute</span><span style="background-color: #f5f5f5; color: #000000;">;</span><span style="background-color: #f5f5f5; color: #ff0000;">
            top</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 150px</span><span style="background-color: #f5f5f5; color: #000000;">;</span><span style="background-color: #f5f5f5; color: #ff0000;">
            left</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 100px</span><span style="background-color: #f5f5f5; color: #000000;">;</span><span style="background-color: #f5f5f5; color: #ff0000;">    
            font-size</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 30px</span><span style="background-color: #f5f5f5; color: #000000;">;</span><span style="background-color: #f5f5f5; color: #ff0000;">
            color</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> #000</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
        <span style="background-color: #f5f5f5; color: #000000;">}</span>
    <span style="color: #0000ff;"></span><span style="color: #800000;">style</span><span style="color: #0000ff;">></span>
<span style="color: #0000ff;"></span><span style="color: #800000;">head</span><span style="color: #0000ff;">></span>
<span style="color: #0000ff;"><span style="color: #800000;">body</span><span style="color: #0000ff;">></span>
    <span style="color: #0000ff;"><span style="color: #800000;">div </span><span style="color: #ff0000;">class</span><span style="color: #0000ff;">="wrap"</span><span style="color: #0000ff;">></span>
        <span style="color: #0000ff;"><span style="color: #800000;">div </span><span style="color: #ff0000;">class</span><span style="color: #0000ff;">="con"</span><span style="color: #0000ff;">></span><span style="color: #800000;">div</span><span style="color: #0000ff;">></span>
        <span style="color: #0000ff;"><span style="color: #800000;">span</span><span style="color: #0000ff;">></span>我爱夏天<span style="color: #0000ff;"></span><span style="color: #800000;">span</span><span style="color: #0000ff;">></span>
    <span style="color: #0000ff;"></span><span style="color: #800000;">div</span><span style="color: #0000ff;">></span>
<span style="color: #0000ff;"></span><span style="color: #800000;">body</span><span style="color: #0000ff;">></span>
<span style="color: #0000ff;"></span><span style="color: #800000;">html</span><span style="color: #0000ff;">></span></span></span></span></span></span></span></span></span></span></span>

最后效果：

解决方法二：

用rgba()设置background的背景色和透明度样式。

    <span style="color: #0000ff;"><span style="color: #800000;">style</span><span style="color: #0000ff;">></span><span style="background-color: #f5f5f5; color: #800000;">
        div</span><span style="background-color: #f5f5f5; color: #000000;">{</span><span style="background-color: #f5f5f5; color: #ff0000;">
            width</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;">300px</span><span style="background-color: #f5f5f5; color: #000000;">;</span><span style="background-color: #f5f5f5; color: #ff0000;">
            height</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 300px</span><span style="background-color: #f5f5f5; color: #000000;">;</span><span style="background-color: #f5f5f5; color: #ff0000;">
            margin</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 50px auto</span><span style="background-color: #f5f5f5; color: #000000;">;</span><span style="background-color: #f5f5f5; color: #ff0000;">
            line-height</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 300px</span><span style="background-color: #f5f5f5; color: #000000;">;</span><span style="background-color: #f5f5f5; color: #ff0000;">
            text-align</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> center</span><span style="background-color: #f5f5f5; color: #000000;">;</span><span style="background-color: #f5f5f5; color: #ff0000;">
            background</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> rgba(250,18,18,0.2)</span><span style="background-color: #f5f5f5; color: #000000;">;</span><span style="background-color: #f5f5f5; color: #ff0000;">
            color</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> #000</span><span style="background-color: #f5f5f5; color: #000000;">;</span><span style="background-color: #f5f5f5; color: #ff0000;">
            font-size</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 30px</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
         
        <span style="background-color: #f5f5f5; color: #000000;">}</span>
    <span style="color: #0000ff;"></span><span style="color: #800000;">style</span><span style="color: #0000ff;">></span></span>

最后效果：

可以明显看出使用CSS3的rgba（）要方便很多，节省大量代码，文档结构也更加清晰，不过rgba（）的兼容性问题也让让人头疼：

最后给出一个兼容性的解决方法：

<span style="color: #000000;">.rgba {
  background: rgb(0,0,0); /*The Fallback color,这里也可以使用一张图片来代替*/
  background: rgba(0, 0, 0,0.5);
  -ms-filter: "progid:DXImageTransform.Microsoft.gradient(GradientType=1,startColorstr=#80000000,endColorstr=#80000000)"; /*Filter for IE8 */    
  filter: progid:DXImageTransform.Microsoft.gradient(GradientType=1,startColorstr=#80000000, endColorstr=#80000000); /*Filter for older IEs */
 }</span>

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