element()

Limited availability

This feature is not Baseline because it does not work in some of the most widely-used browsers.

Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The element() CSS function defines an <image> value generated from an arbitrary HTML element. This image is live, meaning that if the HTML element is changed, the CSS properties using the resulting value are automatically updated.

A particularly useful scenario for using this would be to render an image in an HTML <canvas> element, then use that as a background.

On Gecko browsers, you can use the non-standard document.mozSetImageElement() method to change the element being used as the background for a given CSS background element.

Syntax

css

element(id)

where:

id: The ID of an element to use as the background, specified using the HTML attribute #id on the element.

Formal syntax

<element()> = 
  element( <id-selector> )  

<id-selector> = 
  <hash-token>

Examples

These examples work in builds of Firefox that support -moz-element().

A somewhat realistic example

This example uses a hidden <div> as a background. The background element uses a gradient, but also includes text that is rendered as part of the background.

html

<div id="target-box">
  <p>This box uses the element with the #my-background ID as its background!</p>
</div>

<div id="background-container">
  <div id="my-background">
    <p>This text is part of the background. Cool, huh?</p>
  </div>
</div>

css

#target-box {
  width: 400px;
  height: 400px;
  background: -moz-element(#my-background) no-repeat;
}

#background-container {
  overflow: hidden;
  height: 0;
}

#my-background {
  width: 1024px;
  height: 1024px;
  background-image: linear-gradient(to right, red, orange, yellow, white);
}

#my-background p {
  transform-origin: 0 0;
  rotate: 45deg;
  color: white;
}

The <div> element with the ID "my-background" is used as the background for the content including the paragraph "This box uses the element with the #my-background ID as its background!".

Page Preview

This example based on Vincent De Oliveira's creates a preview of the <div id="css-source"> inside <div id="css-result">.

HTML

html

<div id="css-source">
  <h1>Page Preview</h1>
</div>
<div id="css-result"></div>

CSS

css

#css-result {
  background: -moz-element(#css-source) no-repeat;
  width: 256px;
  height: 32px;
  background-size: 80%;
  border: dashed;
}

Result

Specifications

Specification
CSS Images Module Level 4 # element-notation