使用CSS添加“水印”效果吗？

Question

我在div中有一张图片。我需要在div的图像上方添加水印效果，或者基本上是另一个图像。如何使用CSS做到这一点？

示例代码：

<div id="image">
</div>

css：

#image {
   background:url(images/images.png) no-repeat;
}

Answer 1

至少有两种方法可以做到这一点，@ erenon的回答已触及了其中一种。

为了满足您的要求并使用图像：

<div id="image">
    <img src="path/to/watermarking_image.png" alt="..." />
</div>

使用以下CSS：

#image {
/* the image you want to 'watermark' */
height: 200px; /* or whatever, equal to the image you want 'watermarked' */
width: 200px; /* as above */
background-image: url(path/to/image/to/be/watermarked.png);
background-position: 0 0;
background-repeat: no-repeat;
position: relative;
}

#image img {
/* the actual 'watermark' */
position: absolute;
top: 0; /* or whatever */
left: 0; /* or whatever, position according to taste */
opacity: 0.5; /* Firefox, Chrome, Safari, Opera, IE >= 9 (preview) */
filter:alpha(opacity=50); /* for <= IE 8 */
}

#image {
  /* the image you want to 'watermark' */
  height: 200px;
  /* or whatever, equal to the image you want 'watermarked' */
  width: 200px;
  /* as above */
  background-image: url(https://www.davidrhysthomas.co.uk/linked/astrid_avatar.png);
  background-position: 0 0;
  background-repeat: no-repeat;
  position: relative;
}

#image img {
  /* the actual 'watermark' */
  position: absolute;
  top: 0;
  /* or whatever */
  left: 0;
  /* or whatever, position according to taste */
  opacity: 0.5;
  /* Firefox, Chrome, Safari, Opera, IE >= 9 (preview) */
  filter: alpha(opacity=50);
  /* for <= IE 8 */
}

<div id="image">
  <img src="https://www.davidrhysthomas.co.uk/linked/watermark.png" alt="..." />
</div>

这将生成类似以下内容的内容：

   +--------------+--------------+
   |              |              |
   | 'watermark'  |              |
   |              |        __    |
   +--------------+       /  \   |
   |                     (    )  |
   |               /\     \  /   |
   |              /  \     ||    |   <-- Picture. Of...something. O_o
   | /\          /    \    ||    |
   |/  \________/      \_()||_()(|
   +-----------------------------+

另一种方法是，假设您要对所有水印进行“水印”操作，就是使用words：

<div id="image">
    <p>Watermark text</p>
</div>

以及以下CSS：

#image {
/* the image you want to 'watermark' */
height: 200px; /* or whatever, equal to the image you want 'watermarked' */
width: 200px; /* as above */
background-image: url(path/to/image/to/be/watermarked.png);
background-position: 0 0;
background-repeat: no-repeat;
position: relative;
}

#image p {
/* the actual 'watermark' */
position: absolute;
top: 0; /* or whatever */
left: 0; /* or whatever, position according to taste */
opacity: 0.5; /* Firefox, Chrome, Safari, Opera, IE >= 9 (preview) */
filter:alpha(opacity=50); /* for <= IE 8 */
}

#image {
  width: 200px;
  height: 200px;
  background-image: url(https://www.davidrhysthomas.co.uk/linked/astrid_avatar.png);
  background-position: 0 0;
  background-repeat: no-repeat;
  position: relative;
}

#image p {
  /* the actual 'watermark' */
  position: absolute;
  top: 0;
  /* or whatever */
  left: 0;
  /* or whatever, position according to taste */
  opacity: 0.5;
  /* Firefox, Chrome, Safari, Opera, IE >= 9 (preview) */
  filter: alpha(opacity=50);
  /* for <= IE 8 */
}

<div id="image">
  <p>Watermark text</p>
</div>

这将生成类似以下内容的内容：

   +--------------+--------------+
   |              |              |
   |  watermark   |              |
   |    text      |        __    |
   +--------------+       /  \   |
   |                     (    )  |
   |               /\     \  /   |
   |              /  \     ||    |   <-- Picture. Of...something. O_o
   | /\          /    \    ||    |
   |/  \________/      \_()||_()(|
   +-----------------------------+

我意识到这个问题可能会得到您的满意答复，但我希望这对您有所帮助，即使只是作为一般信息。

已更新为添加SVG选项，但请记住，在此示例中，'水印'文本是可选的，并且可以检查SVG元素以检索图像URL：

svg {
  width: 300px;
  height: 300px;
  border: 2px solid #000;
}

<svg viewBox="0 0 200 200" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
  <style>
    /* adjusting the fill, colour and transparency,
       of the watermark text while the SVG is hovered */
    svg:hover .watermark {
      fill: #666f;
      font-size: 2.1em;
    }
    /* defining the default style of the watermark */
    .watermark {
      fill: #bbbb;
      font-size: 2em;
      font-family: Ubuntu, Calibri, sans-serif;
      font-weight: bold;
      transition: all 0.3s linear;
    }
  </style>
  <!-- the image that you want to be watermarked: -->
  <image xlink:href="http://www.davidrhysthomas.co.uk/linked/astrid_avatar.png" height="200px" width="200px" />
  <!-- the watermark text: -->
  <text x="50%" y="50%" dominant-baseline="middle" text-anchor="middle" class="watermark">watermark</text>
</svg>

Answer 2

您确定要在客户端加水印吗？这样做基本上会破坏拥有水印的整个目的。您要做的是将已经包含水印的图像服务器化。为此，您必须编写服务器端代码。

Answer 3

您的解决方案：

CSS：

#watermark{
   background:url(images/watermark.png) no-repeat; 
   width: 100px;
   height: 100px;
   position: relative;
   top: 0;
   left: 0;
}
#image{
   width: 100px;
   height: 100px;
   position: relative;
   top: 0;
   left: 0;
}

HTML：

<div>
<div id="image"><img src="..." /></div>
<div id="watermark"></div>
</div>

更好的解决方案：

某些人无法突破重叠水印，但有些人可以。强烈建议使用服务器端水印，例如imagemagick lib。

Answer 4

您可能会使用透明的PNG覆盖两个图像，但是您确实希望在服务器上执行此操作，因为基于客户端的解决方案很容易被破坏，并且实际上并不能保护任何内容。