c# - 如何在多边形内旋转位图？

Question

我这样定义了一个多边形:

            <!-- Draws a hexagon by specifying the vertices of a polygon -->
            <Polygon x:Name="polygon"
                     Points="0,50 0,120 50,170 120,170 170,120 170,50 120,0 50,0"
                     Margin="25, 0, 25, 25"
                     Stroke="Red"
                     RenderTransformOrigin="0.5,0.5">

                <Polygon.RenderTransform>
                    <CompositeTransform />
                </Polygon.RenderTransform>

                <Polygon.Fill>
                    <ImageBrush x:Name="imageBrush"
                                ImageSource="Assets/image1.jpg"
                                Stretch="Fill">
                    </ImageBrush>
                </Polygon.Fill>
            </Polygon>

我还定义了这样一个 Storyboard:

    <Storyboard x:Name="Storyboard2">
        <DoubleAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.RenderTransform).(CompositeTransform.Rotation)"
                                       Storyboard.TargetName="polygon">
            <EasingDoubleKeyFrame KeyTime="0"
                                  Value="0" />
            <EasingDoubleKeyFrame KeyTime="0:0:2"
                                  Value="-360" />
        </DoubleAnimationUsingKeyFrames>
    </Storyboard>

我这样开始多边形旋转:

        Storyboard2.BeginTime = new TimeSpan( 0 );
        Storyboard2.Begin();

上面的代码按预期旋转了整个多边形。但是我想修改它，让多边形静止不动，只在多边形内旋转位图。

我该怎么做？谢谢

Answer 1

要在多边形内旋转图像，您可以尝试使用 ImageBrush.RelativeTransform property像下面这样:

<Polygon x:Name="polygon"
         Margin="25, 0, 25, 25"
         Points="0,50 0,120 50,170 120,170 170,120 170,50 120,0 50,0"
         Stroke="Red">
    <Polygon.Fill>
        <ImageBrush x:Name="imageBrush" ImageSource="Assets/Capture.PNG" Stretch="Fill">
            <ImageBrush.RelativeTransform>
                <CompositeTransform CenterX="0.5" CenterY="0.5" />
            </ImageBrush.RelativeTransform>
        </ImageBrush>
    </Polygon.Fill>
</Polygon>

然后像下面这样改变你的Storyboard:

<Storyboard x:Name="Storyboard2">
    <DoubleAnimationUsingKeyFrames EnableDependentAnimation="True"
                                   Storyboard.TargetName="imageBrush"
                                   Storyboard.TargetProperty="(Brush.RelativeTransform).(CompositeTransform.Rotation)">
        <EasingDoubleKeyFrame KeyTime="0" Value="0" />
        <EasingDoubleKeyFrame KeyTime="0:0:2" Value="-360" />
    </DoubleAnimationUsingKeyFrames>
</Storyboard>

这里，由于目标是ImageBrush，所以我们需要将Storyboard.TargetProperty改为(Brush.RelativeTransform).(CompositeTransform.Rotation)。由于动画以 Brush.RelativeTransform 为目标，因此它是一个依赖动画。我们需要将 EnableDependentAnimation 属性设置为 true 以启用此动画。更多依赖动画请看Dependent and independent animations .

在此之后，您可以调用 Storyboard2.Begin(); 开始动画。