Easing Animation(缓动动画)

namespace Easing2
{


    //EasingFunctionBase 为所有缓动函数提供基类
    class CustomPowerEase : EasingFunctionBase
    {
      
        // Using a DependencyProperty as the backing store for Power.
// This enables animation, styling, binding, etc...

// UIPropertyMetadata(object DefaultValue)用属性的指定默认值初始化 System.Windows.UIPropertyMetadata 类的新实例。

        public static readonly DependencyProperty PowerProperty =
            DependencyProperty.Register("Power", typeof(double), typeof(CustomPowerEase), new UIPropertyMetadata(6.0));

        //添加属性包装器
        public double Power
        {
            get { return (double)GetValue(PowerProperty); }
            set { SetValue(PowerProperty, value); }
        }

        //System.Windows.Freezable, 定义一个对象，该对象具有可修改状态和只读（冻结）状态。
//派生自 System.Windows.Freezable 的类提供详细的更改通知，可以是不可变的，并且可以进行自我克隆。
        protected override System.Windows.Freezable CreateInstanceCore()
        {
            return new CustomPowerEase();
        }

        protected override double EaseInCore(double normalizedTime)
        {
            //Math.Pow(double x,double y)返回指定数字的指定次幂
            return Math.Pow(normalizedTime, Power);
        }
    }
}

<Window x:Class="Easing2.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:Easing2"
        Title="MainWindow" Height="350" Width="525">

    <Window.Resources>
        <Storyboard x:Key="AnimateTarget">
            <!--Storyboard.TargetName,获取或设置要进行动画处理的对象的名称。
                Storyboard.TargetProperty,获取或设置应进行动画处理的属性。-->
            
            <DoubleAnimationUsingKeyFrames Storyboard.TargetName="Transform" Storyboard.TargetProperty="X">
                <!--EasingDoubleKeyFrame类，通过它可以将缓动函数与 DoubleAnimationUsingKeyFrames 关键帧动画相关联-->
                <EasingDoubleKeyFrame KeyTime="0:0:0" Value="0.0">
                    <!--EasingDoubleKeyFrame,Value获取或设置关键帧的目标值。-->
                </EasingDoubleKeyFrame>

                <EasingDoubleKeyFrame KeyTime="0:0:4" Value="100.0">
                    <!--EasingDoubleKeyFrame.EasingFunction获取或设置应用于关键帧的缓动函数。-->
                    <EasingDoubleKeyFrame.EasingFunction>
                        <!--这里使用了DP Power-->
                        <local:CustomPowerEase Power="20" />
                    </EasingDoubleKeyFrame.EasingFunction>
                </EasingDoubleKeyFrame>

            </DoubleAnimationUsingKeyFrames>

            <DoubleAnimationUsingKeyFrames Storyboard.TargetName="Transform"  Storyboard.TargetProperty="Y">

                <EasingDoubleKeyFrame KeyTime="0:0:0" Value="0.0">
                </EasingDoubleKeyFrame>

                <EasingDoubleKeyFrame KeyTime="0:0:4"   Value="100.0">

                    <EasingDoubleKeyFrame.EasingFunction>
                        
                        <!--<PowerEase EasingMode="EaseIn" Power="5"/>-->
                        <!--PowerEase.EaseInCore,此成员重写 EasingFunctionBase.EaseInCore(Double)，
                        提供缓动函数的逻辑部分，通过重写此部分可以生成自定义缓动函数的 EaseIn 模式。
-->
                        <local:CustomPowerEase Power="10" />
                    </EasingDoubleKeyFrame.EasingFunction>

                </EasingDoubleKeyFrame>
            </DoubleAnimationUsingKeyFrames>

        </Storyboard>
    </Window.Resources>

    <Grid>
        <Rectangle Width="20"  Height="20"  Fill="Red"  RenderTransformOrigin="0.5, 0.5">
            <Rectangle.RenderTransform>
                <TranslateTransform x:Name="Transform" />
            </Rectangle.RenderTransform>
        </Rectangle>

        <Button Width="100" Height="40" Content="Start Animation" Click="Button_Click"
                HorizontalAlignment="Center"
                VerticalAlignment="Bottom" />
    </Grid>
</Window>

private void Button_Click(object sender, RoutedEventArgs e)
        {
            ((Storyboard)this.Resources["AnimateTarget"]).Begin();
        }