实现这样的效果需要使用OpacityMask。下面的示例使用了一个设置为Tile的VisualBrush作为遮罩,并使用刷子的transform属性来实现您所描述的动画效果。
<Window
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" mc:Ignorable="d" x:Class="WpfApplication1.MainWindow"
Title="MainWindow" Height="447" Width="569">
<Window.Resources>
<Storyboard x:Key="Wave">
<DoubleAnimation Storyboard.TargetProperty="(UIElement.OpacityMask).(Brush.RelativeTransform).(TransformGroup.Children)[3].(TranslateTransform.X)" Storyboard.TargetName="ellipse" RepeatBehavior="Forever" From="0" To="1" Duration="0:0:1" />
</Storyboard>
</Window.Resources>
<Window.Triggers>
<EventTrigger RoutedEvent="FrameworkElement.Loaded">
<BeginStoryboard Storyboard="{StaticResource Wave}"/>
</EventTrigger>
</Window.Triggers>
<Canvas>
<Ellipse x:Name="ellipse" Fill="#FF82C6FF" Height="160" Canvas.Left="320" Canvas.Top="80" Width="160">
<Ellipse.OpacityMask>
<VisualBrush Visual="{Binding ElementName=wave}" TileMode="Tile" Viewport="0,-1,1,3" Stretch="None" >
<VisualBrush.RelativeTransform>
<TransformGroup>
<ScaleTransform />
<SkewTransform/>
<RotateTransform/>
<TranslateTransform Y="{Binding Value,ElementName=y}" />
</TransformGroup>
</VisualBrush.RelativeTransform>
</VisualBrush>
</Ellipse.OpacityMask>
</Ellipse>
<Grid x:Name="wave" Height="377" Canvas.Left="80" Canvas.Top="23" Width="160" Background="#00000000">
<Grid.RowDefinitions>
<RowDefinition Height="1*"/>
<RowDefinition Height="{Binding Value,ElementName=amplitude}"/>
<RowDefinition Height="1*"/>
</Grid.RowDefinitions>
<Path Fill="#FF82C6FF" Data="M12.5,1.6925709 C31.25,1.6925709 31.25,18.615654 50,18.615654 68.75,18.615654 68.75,1.6925709 87.5,1.6925709 87.499909,27.077196 87.5,27.077107 87.5,27.077107 63.28125,27.077136 12.5,27.077196 12.5,27.077196 12.5,27.077196 12.500094,27.077196 12.5,1.6925709 z" Stretch="Fill" Grid.Row="1"/>
<Rectangle Fill="#FF82C6FF" Grid.Row="2" Margin="0,-1,0,0" />
</Grid>
<Slider x:Name="y" Width="200" Minimum="-0.6" Maximum="1" Value="0"/>
<Slider x:Name="amplitude" Width="200" Minimum="1" Maximum="100" Value="20" Canvas.Top="23"/>
</Canvas>
</Window>
为了隐藏遮罩层,你可以直接将其放置在VisualBrush内,而不是像上面那样使用绑定。你可能还想查看其他类型的画笔以及它们的转换和视区/视图框。更新:现在遮罩层分为两部分,可以分别调整波幅。你也可以调整ScaleTransform.ScaleX来改变频率,但你需要确保你得到整个波形,否则动画会卡顿。例如,请尝试0.5、0.25、0.1。