$fondo: url(/grid/assets/img/backimage.png);    
{ padding: 0; margin: 0; } 
body { 
    ::before{
        content:"" ; height: 1008px; width: 100%; display: flex; position: absolute; 
        background-image: $fondo ; background-repeat: no-repeat ; background-position: 
        center; background-size: cover; filter: blur(1.6rem);
    }
}

CSS网格对我来说更容易理解。：）

html, body { width: 100%; height: 100%; } .container { width: 100%; height: 100%; display: grid; grid-template-columns: 1fr 6fr 1fr; grid-template-rows: 1fr 6fr 1fr; grid-template-areas: '. . .' '. content .' '. . .'; justify-content: center; align-items: center; } .backbround { width: 100%; height: 100%; grid-area: 1/1/5/5; background-image: url(https://i.imgur.com/aUhpEz3.jpg); filter: blur(5px); background-position: center; background-repeat: no-repeat; background-size: cover; } .content { height: 200px; position: relative; grid-area: content; display: flex; justify-content: center; align-items: center; color: white; } <div class="container"> <div class="backbround"></div> <div class="content"><h1>Hello World</h1></div> </div>

为此，您需要重新构造HTML。为了模糊背景，你必须模糊整个元素。如果你只想模糊背景，它必须是它自己的元素。

现在，通过使用CSS GRID，这变得更加简单和灵活。你只需要将模糊的背景(imgbg)与文本(h2)重叠即可。

<div class="container">
 <div class="imgbg"></div>
 <h2>
  Lorem ipsum dolor sit amet consectetur, adipisicing elit. Facilis enim
  aut rerum mollitia quas voluptas delectus facere magni cum unde?:)
 </h2>
</div>

还有css:

.container {
        display: grid;
        width: 30em;
      }

.imgbg {
        background: url(bg3.jpg) no-repeat center;
        background-size: cover;
        grid-column: 1/-1;
        grid-row: 1/-1;
        filter: blur(4px);
      }


     .container h2 {
        text-transform: uppercase;
        grid-column: 1/-1;
        grid-row: 1/-1;
        z-index: 2;
      }

看看这支笔。

您必须使用两个不同的容器，一个用于背景图像，另一个用于内容。

在本例中，我创建了两个容器，.background-image和.content。

它们都被放置在位置:固定和左:0;右:0;。显示它们的差异来自为元素设置的不同的z-index值。

.background-image { position: fixed; left: 0; right: 0; z-index: 1; display: block; background-image: url('https://i.imgur.com/lL6tQfy.png'); width: 1200px; height: 800px; -webkit-filter: blur(5px); -moz-filter: blur(5px); -o-filter: blur(5px); -ms-filter: blur(5px); filter: blur(5px); } .content { position: fixed; left: 0; right: 0; z-index: 9999; margin-left: 20px; margin-right: 20px; } <div class="background-image"></div> <div class="content"> <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Duis aliquam erat in ante malesuada, facilisis semper nulla semper. Phasellus sapien neque, faucibus in malesuada quis, lacinia et libero. Sed sed turpis tellus. Etiam ac aliquam tortor, eleifend rhoncus metus. Ut turpis massa, sollicitudin sit amet molestie a, posuere sit amet nisl. Mauris tincidunt cursus posuere. Nam commodo libero quis lacus sodales, nec feugiat ante posuere. Donec pulvinar auctor commodo. Donec egestas diam ut mi adipiscing, quis lacinia mauris condimentum. Quisque quis odio venenatis, venenatis nisi a, vehicula ipsum. Etiam at nisl eu felis vulputate porta.</p> <p>Fusce ut placerat eros. Aliquam consequat in augue sed convallis. Donec orci urna, tincidunt vel dui at, elementum semper dolor. Donec tincidunt risus sed magna dictum, quis luctus metus volutpat. Donec accumsan et nunc vulputate accumsan. Vestibulum tempor, erat in mattis fringilla, elit urna ornare nunc, vel pretium elit sem quis orci. Vivamus condimentum dictum tempor. Nam at est ante. Sed lobortis et lorem in sagittis. In suscipit in est et vehicula.</p> </div>

为Lorem Ipsum的文本道歉。

更新

感谢Matthew Wilcoxson在https://codepen.io/akademy/pen/FlkzB之前使用.content::提供了更好的实现

$fondo: url(/grid/assets/img/backimage.png);    
{ padding: 0; margin: 0; } 
body { 
    ::before{
        content:"" ; height: 1008px; width: 100%; display: flex; position: absolute; 
        background-image: $fondo ; background-repeat: no-repeat ; background-position: 
        center; background-size: cover; filter: blur(1.6rem);
    }
}