如何在不透明的图像顶部添加黑色图层

Question

我想知道是否有一种方法可以在我的图像上添加一个黑色层，但让它稍微透明，这样您仍然可以看到图像。

我正在使用 Bootstrap 4 & 下面是我正在使用的代码，包括 CSS :)

任何帮助将不胜感激。谢谢

<div class="row">
  <div class="col-md-6">    
    <div class="card-overlay" style="background-image: url('img/dirt1.jpg')">
      <div class="white-text text-center">
        <div class="card-block">
          <h3>Project title</h3>
          <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Repellat 
 fugiat, laboriosam, voluptatem, optio vero odio nam sit officia accusamus 
 minus error nisi architecto nulla ipsum dignissimos. Odit
            sed qui, dolorum!.
          </p>
          <a class="btn btn-primary" href="...">Read More</a>
        </div>
      </div>
    </div> 
  </div>
</div>

CSS:

.card-overlay {
  background: rgba(0, 0, 0, 0.5);
}

Answer 1

试试这个：

.card-overlay {position:relative;}
.card-overlay:before{    background: rgba(37, 35, 35, 0.07);    position: absolute;    height: 100%;    left: 0;    top: 0;    margin: 0;    width: 100%;    content: ' ';    display: block;}

Answer 2

您必须将 .car-overlay div 放在带有背景的 div 中。这是因为如果一个元素有背景图片和背景颜色，那么背景颜色会出现在背景图片后面。

.card-overlay {
  background: rgba(0, 0, 0, 0.5);
}

<div class="row">
  <div class="col-md-6">
    <div style="background-image: url('https://www.placecage.com/c/460/300');background-size:cover;">
      <div class="card-overlay">
        <div class="white-text text-center">
          <div class="card-block">
              <h3>Project title</h3>
              <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Repellat fugiat, laboriosam, voluptatem, optio vero odio nam sit officia accusamus minus error nisi architecto nulla ipsum dignissimos. Odit
                  sed qui, dolorum!.</p>
               <a class="btn btn-primary" href="...">Read More</a>
         </div>
        </div>
      </div>
    </div>
  </div>
</div>

如果您不想更改 HTML 结构，您可以使用 CSS3 具有渐变而不是背景颜色的多重背景，因为您无法对背景颜色进行分层。

.card-overlay {
  background:
  linear-gradient(
    rgba(0, 0, 0, 0.5),
    rgba(0, 0, 0, 0.5)
  ),
  url('https://www.placecage.com/c/460/300');
}

<div class="row">
  <div class="col-md-6">
    <div class="card-overlay">
        <div class="white-text text-center">
          <div class="card-block">
              <h3>Project title</h3>
              <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Repellat
       fugiat, laboriosam, voluptatem, optio vero odio nam sit officia accusamus
       minus error nisi architecto nulla ipsum dignissimos. Odit
                  sed qui, dolorum!.</p>
               <a class="btn btn-primary" href="...">Read More</a>
         </div>
      </div>
    </div>
  </div>
</div>

Answer 3

你可以用 after/before 来做这个

.card-overlay{
  position: relative;
}
.card-overlay:after {
  content:'';
  position:absolute;
  left:0px;
  top:0px;
  width:100%;
  height:100%;
  background: rgba(0, 0, 0, 0.5);
}

Answer 4

CSS

.container { background-color: #000000;}
.container img { opacity: 0.2; }

HTML

<div class="container">
<img src="#">
</div>

Working Fiddle Example Here...

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