SVG Animation

原文：http://tutorials.jenkov.com/svg/index.html

http://tutorials.jenkov.com/svg/svg-animation.html

SVG Animation

• SVG Animation Example
• Overview of Animation Options
• set
  • attributeType
• animate
• animateTransform
• animateMotion
• Time Units
• Coordinating Animations
• Repeating Animations
• Combining Animations

It is possible to animate the shapes in an SVG image. There are several different ways to animate SVG shapes. In this text I will go through the various possibilities.

SVG Animation Example

Here is a simple SVG animation example:

<svg xmlns="http://www.w3.org/2000/svg"
    xmlns:xlink="http://www.w3.org/1999/xlink">

    <rect x="10" y="10" height="110" width="110"
         style="stroke:#ff0000; fill: #0000ff">

        <animateTransform
            attributeName="transform"
            begin="0s"
            dur="20s"
            type="rotate"
            from="0 60 60"
            to="360 60 60"
            repeatCount="indefinite"
        />
    </rect>

</svg>

Notice how the <rect> element has a <animateTransform> element nested inside it. It is this element that animates the rectangle.

Here is the resulting SVG animation:

Overview of Animation Options

Animation is done by manipulating the attributes of shapes over time. This is done using one or more of the 5 SVG animation elements:

1. <set>
2. <animate>
3. <animateColor>
4. <animateTransform>
5. <animateMotion>

Each of these SVG animation elements sets or animates different aspects of SVG shapes. These animation elements are explained throughout the rest of this text.

set

The set element is the simplest of the SVG animation elements. It simply sets an attribute to a certain value after a specific time interval has passed. As such, the shape is not continuously animating, but just changes attribute value once.

Here is a <set> element example:

<circle cx="30" cy="30" r="25" style="stroke: none; fill: #0000ff;">
    <set attributeName="r" attributeType="XML"
         to="100"
         begin="0s"  />

</circle>

Notice the <set> element nested inside the circle element. This is how the <set> element is applied to a shape - by nesting it inside the SVG element of the shape you want to apply it to.

The <set> element sets the value of an attribute at a certain time. The name of the attribute to set is specified inside the attributeName attribute. The value to set it to is specified inside the to attribute. The time to set the attribute value is specified inside the begin attribute.

The example above sets the attribute r to 100 after 5 seconds. Here is the resulting image:

attributeType

The previous example also had an attributeType attribute inside the <set> element. The value was set to XML. That is because the attribute to set a value for in the example (the r attribute) is an attribute of the SVG circle element. Since SVG elements are XML elements, SVG attributes are XML attributes.

You can also animate CSS properties of a shape. If you do so, you will need to set the attributeType to CSS. If you do not provide an attributeType attribute, then the browser will try to guess if the attribute to animate is an XML attribute or CSS property.

animate

The animate element is used to animate an attribute of an SVG shape. You nest the animate element inside the shape you want it applied to. Here is an example:

<circle cx="30" cy="30" r="25" style="stroke: none; fill: #0000ff;">
    <animate attributeName="cx" attributeType="XML"
             from="30"  to="470"
             begin="0s" dur="5s"
             fill="remove" repeatCount="indefinite"/>

</circle>

This example animates the cx attribute of the <circle> element from a value of 30 (the from attribute) to a value of 479 (the to attribute). The animation starts at 0 seconds (the begin attribute) and has a duration of 5 seconds (the dur attribute).

When the animation is finished the animated attribute is set back to its original value (the fill="remove"attribute setting). If you wanted the animated attribute to keep the to-value of the animation, set the fillattribute to freeze. The animation repeats indefinitely (the repeatCount attribute).

Here is the resulting animation:

animateTransform

The <animateTransform element can animate the transform attribute of a shape. The <animate> element cannot do that.

Here is an example:

<rect x="20" y="20" width="100" height="40"
    style="stroke: #ff00ff; fill:none;" >
  <animateTransform attributeName="transform"
                    type="rotate"
                    from="0 100 100" to="360 100 100"
                    begin="0s" dur="10s"
                    repeatCount="indefinite"
          />
</rect>

This <animateTransform> example animates the transform attribute of the <rect> element it is nested inside. The type attribute is set to rotate (the rotate transform function) meaning the animated transformation will be a rotation. The from and to attributes set the parameters to be animated and passed to the rotate function. This example rotates from a degree of 0 to a degree of 360 around the point 100,100 .

Here is an example that animates the scale of a square:

<rect x="20" y="20" width="40" height="40"
      style="stroke: #ff00ff; fill: none;" >
    <animateTransform attributeName="transform"
                      type="scale"
                      from="1 1" to="2 3"
                      begin="0s" dur="10s"
                      repeatCount="indefinite"
            />
</rect>

Notice again that the from and to attributes contain the values you would normally pass as parameters to the scale() transform function.

Here is the resulting animation:

animateMotion

The <animateMotion> element can animate the movement of a shape along a path. It can also rotate the shape to match the slope of the path, like a car driving up and down hill. Here is an example:

  <rect x="0" y="0" width="30" height="15"
        style="stroke: #ff0000; fill: none;">
      <animateMotion
              path="M10,50 q60,50 100,0 q60,-50 100,0"
              begin="0s" dur="10s" repeatCount="indefinite"
              />
  </rect>

The path to animate the rectangle along is specified in the path attribute of the <animateMotion> element. The path attribute uses the same syntax as the path element.

Here is the resulting animation with the path shown too, so you can better follow the motion.

In order to rotate the square to align with the slope of the path, you set the rotate attribute of the <animateMotion> element to auto. Here is an example:

  <rect x="0" y="0" width="30" height="15"
        style="stroke: #ff0000; fill: none;">
      <animateMotion
              path="M10,50 q60,50 100,0 q60,-50 100,0"
              begin="0s" dur="10s" repeatCount="indefinite"
              rotate="auto"
              />
  </rect>

Here is the resulting animation. Notice how the rotation of the square changes to fit the path.

You can also set the rotate attribute to a specific value, like 20 or 30 etc. That will keep the shape rotated that number of degrees throughout the animation.

Time Units

When you define an SVG animation you specify when the animation start time and duration. When specifying that, you have the choice between different time units. The time units are typically specified inside the begin, dur and end attributes of the various animation elements.

Inside these attributes you can specify a number followed by a time unit, as done in the examples in this text. For instance 5s means 5 seconds. Here is a list of the time units you can use:

Time Unit	Description
h	Hours
min	Minutes
s	Seconds
ms	Milliseconds

You can also specify time in a time format which contain both hours, minutes and seconds. Here is how the format looks like:

hh:mm:ss

Here is an example:

1:30:45

This example specifies a time of 1 hour, 30 minutes and 45 seconds (which is of course very long time for an animation).

Coordinating Animations

You can synchronize the beginning of one animation to the end of another. You do so like this:

<rect x="0" y="0" width="30" height="15"
      style="stroke: #ff0000; fill: none;">

    <animate id="one"
             attributeName="x" attributeType="XML"
             from="0" to="400"
             begin="0s" dur="10s" fill="freeze"
            />
    <animate
            attributeName="y" attributeType="XML"
            from="0" to="50"
            begin="one.end" dur="10s" fill="freeze"
            />
</rect>

Here is the resulting animation:

The first animation has its id attribute set to one.

The second animation references the first animation via its begin attribute. The begin attribute value is set to one.end which means that this animation should start when the animation with the id one ends.

You can use the id.begin or id.end to start an animation when another animation starts or ends. Instead of iduse the ID of the animation element to synchronize to.

You can also specify offsets to the start or end time of another animation, like this:

one.begin+10s

one.end+5s

Additionally you can specify an explicit end time in an animations end attribute. This does not replace the durattribute. All it does is to add another possible end to an animation, so whichever occurs first. Here is an example:

<animate
        attributeName="y" attributeType="XML"
        from="0" to="50"
        begin="one.begin+3s" dur="10s" end="one.end"
        fill="freeze"
        />

This animation will have a duration of 10 seconds, or stop when the animation with the ID one ends, whichever occurs first.

Repeating Animations

There are two attributes you can use inside an animation element which are used to repeat the animation.

The first attribute is the repeatCount attribute. Inside this attribute you can set a number, which will be repeat the animation that number of times, or the value indefinite which will keep the animation running without ever stopping.

The second attribute is the repeatDur which specifies a duration for which the animation is to be repeated. You can also use the value indefinite inside the repeatDur attribute, and the effect is the same as using it inside the repeatCount attribute.

Here are two examples:

<animate
        attributeName="y" attributeType="XML"
        from="0" to="50"
        begin="one.begin+3s" dur="10s"
        repeatCount="3"
        fill="freeze"
        />

<animate
        attributeName="y" attributeType="XML"
        from="0" to="50"
        begin="one.begin+3s" dur="10s"
        repeatDur="30s"
        fill="freeze"
        />

Combining Animations

You can combine animations by listing more than one <animation> inside the element to animate. You have already seen that, but here is another example:

<rect x="10" y="10" width="40" height="20"
     style="stroke: #000000; fill: none;">
   <animate attributeName="x"
            attributeType="XML"
            from="10" to="400"
            begin="0s" dur="10s"
            repeatCount="indefinite"
           />
   <animate attributeName="y"
            attributeType="XML"
            from="10" to="100"
            begin="0s" dur="10s"
            fill="freeze"
            repeatCount="indefinite"
           />
</rect>

This example has two animations, each animating the x and y attributes of the rectangle. Here is the resulting animation:

When combining <animateTransform> elements, the default behaviour is for the second animation to cancel out the first. However, you can combine the transformation animations by adding the attribute additive with a value of sum to both <animateTransform> elements. Here is an example:

<rect x="10" y="10" width="40" height="20"
      style="stroke: #000000; fill: none;">
    <animateTransform attributeName="transform" attributeType="XML"
                      type="scale"
                      from="1" to="3"
                      begin="0s" dur="10s"
                      repeatCount="indefinite"
                      additive="sum"
            />
    <animateTransform attributeName="transform" attributeType="XML"
                      type="rotate"
                      from="0 30 20" to="360 30 20"
                      begin="0s" dur="10s"
                      fill="freeze"
                      repeatCount="indefinite"
                      additive="sum"
            />

Here is the resulting animation which both scales and rotates a rectangle:

Next: SVG Scripting