SVG animation

Animation of Scalable Vector Graphics, an open XML-based standard vector graphics format, is possible through various means:

• Scripting: ECMAScript is a primary means of creating animations and interactive user interfaces within SVG.
• Styling: Since 2008, the development of CSS Animations as a feature in WebKit has made possible stylesheet-driven implicit animation of SVG files from within the Document Object Model (DOM).
• SMIL: Synchronized Multimedia Integration Language, a recommended means of animating SVG-based hypermedia is currently supported by the Safari, Opera, Mozilla Firefox, Google Chrome and Amaya web browsers, as will any browser that aims to pass the Acid3 web standards test as this requires SMIL support for tests 75 and 76. Libraries have also been written as a shim to give current SVG-enabled browsers SMIL support. This method is also known as SVG+Time.

Because SVG supports PNG and JPEG raster images, it can be used to animate such images as an alternative to APNG and Multiple-image Network Graphics.

History

SVG animation elements were developed in collaboration with the W3C Synchronized Multimedia Working Group, developers of the Synchronized Multimedia Integration LanguageSMIL 3.0 Specification SMIL. The SYMM Working Group, in collaboration with the SVG Working Group, has authored the SMIL Animation specification, which represents a general-purpose XML animation feature set. SVG incorporates the animation features defined in the SMIL Animation specification and provides some SVG specific extensions.

SVG in HTML

The SVG can be embedded into HTML with the <img> tag element. By using the src attribute in the image tag it is possible to refer to an SVG file. This only works sometimes and not compatible for old browsers.

Solution for browser compatibility

The most common solution is to use the <object> element, with the data attribute referencing the SVG file. When a browser does not support this, it falls back to the content inside the <object>. This could be a rasterized fallback <img>. This method gives a vector image with an alternative rasterized image for browsers that don’t support SVG.

The downside is that both formats need to be managed, and some browsers will download both the SVG and the rasterized version, becoming a performance problem.

Solution for performance problem

Using inline SVG combined with an SVG <image> element solve the performance problem. This has an SVG href pointing to the vector SVG representation and a src attribute to the rasterized version. Older browsers will rewrite the <image> element as <img> and use the rasterized src attribute, but modern browsers will show the vector SVG.

Which method is best depends on which browser the developer chooses to support, and severity of performance issues.

Libraries to get started

There are several libraries for starting out with SVG animation. They also abstract all browser compatibility issues.

• Velocity.js
• Raphaël
• Snap.svg
• svg.js

Examples

The following code snippets demonstrate three techniques to create animated SVG on compatible browsers. The relevant parts are in bold green.

SVG animation using SMIL

  <!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">  <svg version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"   width="100%" height="100%" viewBox="-4 -4 8 8">   <title>SVG animation using SMIL</title>   <circle cx="0" cy="1" r="2" stroke="red" fill="none">    <animateTransform     attributeName="transform"     attributeType="XML"     type="rotate"     from="0"     to="360"     begin="0s"     dur="1s"     repeatCount="indefinite"/>   </circle>  </svg>  

SVG animation using CSS

  <!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">  <svg version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"   width="100%" height="100%" viewBox="-4 -4 8 8">   <title>SVG animation using CSS</title>   <style type="text/css">    @keyframes         rot_kf { from { transform:         rotate(0deg);   }                                to   { transform:         rotate(360deg); } }    @-moz-keyframes    rot_kf { from { -moz-transform:    rotate(0deg);   }                                to   { -moz-transform:    rotate(360deg); } }    @-webkit-keyframes rot_kf { from { -webkit-transform: rotate(0deg);   }                                to   { -webkit-transform: rotate(360deg); } }    .rot { animation:         rot_kf 1s linear infinite;           -moz-animation:    rot_kf 1s linear infinite;           -webkit-animation: rot_kf 1s linear infinite; }   </style>   <circle class="rot" cx="0" cy="1" r="2" stroke="blue" fill="none"/>  </svg>  

Note: the -moz and -webkit styles are pre-CSS3 browser-specific styles.

SVG animation using ECMAScript

  <!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">  <svg version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"   width="100%" height="100%" viewBox="-4 -4 8 8" onload="rotate(evt)">   <title>SVG animation using ECMAScript</title>   <script type="text/ecmascript">    function rotate(evt) {     var object = evt.target.ownerDocument.getElementById('rot');     setInterval(function () {       var now          = new Date();       var milliseconds = now.getTime() % 1000;       var degrees      = milliseconds * 0.36; // 360 degrees in 1000 ms       object.setAttribute('transform', 'rotate(' + degrees + ')');      }, 20);    }   </script>   <circle id="rot" cx="0" cy="1" r="2" stroke="green" fill="none"/>  </svg>  

Authoring tools

Conversion tools

There are some tools like Google Swiffy which can convert SWF, including Flash animations to SVG animations. Swiffy uses Javascript to animate the SVGs it produces, which are not stored as such on disk, but serialized as JSON.

SMIL attributes to identify the target attribute

The following are the animation attribute which identify the target attribute for the given target element whose value changes over time.

attributeName = "<attributeName>"

Specifies the name of the target attribute. An XMLNS prefix may be used to indicate the XML namespace for the attribute. The prefix will be interpreted in the scope of the current animation element.

attributeType = "CSS | XML | auto"

Specifies the namespace in which the target attribute and its associated values are defined.

• CSS

This specifies that the value of ‘attributeName’ is the name of a CSS property defined as animatable in this specification.

• XML

This specifies that the value of ‘attributeName’ is the name of an XML attribute defined in the default XML namespace for the target element. The attribute must be defined as animatable in this specification.

• auto

The default value is 'auto'. The implementation should match the ‘attribute Name’ to an attribute for the target element. The implementation must first search through the list of CSS properties for a matching property name, and if none is found, search the default XML namespace for the element.

Note: MediaWiki automatically generates static, non-animated thumbnails of SVG images. Viewing the actual .svg image from each respective description page will show its animation in a compatible browser.