CSS - element

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.

Examples

Example1

These examples can be viewed live 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.

<div style="width:400px; height:400px; background:-moz-element(#myBackground1) no-repeat;">
  <p>This box uses the element with the #myBackground1 ID as its background!</p>
</div>

<div style="overflow:hidden; height:0;">
  <div id="myBackground1" style="width:1024px; height:1024px; background-image: linear-gradient(to right, red, orange, yellow, white);">
  <p style="transform-origin:0 0; transform: rotate(45deg); color:white;">This text is part of the background. Cool, huh?</p>
  </div>
</div>

The <div> element with the ID "myBackground1" is used as the background for the content including the paragraph "This box uses the element with the #myBackground1 ID as its background!".

example1.png

A somewhat more bizarre example

This example uses a hidden <button> element in a repeating pattern as its background. This demonstrates that you can use arbitrary elements as background, but doesn't necessarily demonstrate good design practices.

<div style="width:400px; height:100px; background:-moz-element(#myBackground2);">
</div>

<div style="overflow:hidden; height:0;">
  <button id="myBackground2" type="button">Evil button!</button>
</div>

example2.png

Syntax  

element( id )

where:

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

Description  

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.

Browser Compatibility  

Feature Firefox (Gecko) Chrome Internet Explorer Opera Safari
Basic support 4.0 (2.0) [*] -moz No support No support No support No support
Feature Firefox Mobile (Gecko) Android IE Phone Opera Mobile Safari Mobile
Basic support 4.0 (2.0) [*] -moz No support No support No support No support

[*] Usage limited to the background and background-image CSS properties.

See Also  

Specifications  

Specification Status Comment
CSS Image Values and Replaced Content Module Level 4
The definition of 'Using Elements as Images: the element() notation' in that specification.
Working Draft Actually now deferred to CSS4.

License

© 2016 Mozilla Contributors
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-us/docs/web/css/element