WPF移动不规则渐变色窗体

要移动窗体，需要在窗体的MouseDown事件中添加如下代码：

        void Window1_MouseDown(object sender, MouseButtonEventArgs e)
        {
            if (e.LeftButton == MouseButtonState.Pressed)
            {
                DragMove();
            }
        }

<Window x:Class="welcome.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Window1" Background="{x:Null}" Height="395" Width="667" WindowStyle="None" AllowsTransparency="True">
   <Canvas Height="395" Width="667">
        <Path Stroke="DarkGray" StrokeThickness="1" Canvas.Left="0" Width="667" Height="395">
            <Path.Data>
                <PathGeometry>
                    <PathFigure StartPoint="0,20" IsClosed="True">
                        <LineSegment Point="0,375"></LineSegment>
                        <ArcSegment Point="20,395" Size="20,20" ></ArcSegment>
                        <LineSegment Point="647,395"></LineSegment>
                        <ArcSegment Point="667,375" Size="20,20"></ArcSegment>
                        <LineSegment Point="667,20"></LineSegment>
                        <ArcSegment Point="647,0" Size="20,20"></ArcSegment>
                        <LineSegment Point="20,0"></LineSegment>
                        <ArcSegment Point="0,20" Size="20,20"></ArcSegment>
                    </PathFigure>
                </PathGeometry>
            </Path.Data>
            <Path.Fill>
                <LinearGradientBrush StartPoint="0,0" EndPoint="1,1">
                    <GradientStop Color="LightYellow"  Offset="0.25"></GradientStop>
                    <GradientStop Color="Yellow" Offset="0.5"></GradientStop>
                    <GradientStop Color="Orange" Offset="0.75"></GradientStop>
                    <GradientStop Color="OrangeRed" Offset="1"></GradientStop>
                </LinearGradientBrush>
            </Path.Fill>
        </Path>
    </Canvas>
</Window>