Canvasの半透明のコピーを表示

ボタンをクリックすると、Rectangleクラスのインスタンスを新たに生成し、コピー対象のCanvasのVisualBrushで塗りつぶして表示しています。
表示する座標は、Canvas.SetTop、Canvas.SetLeft で指定します。

MainWindow.xaml

<Window x:Class="WpfApplication4.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Height="200" Width="200">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto" />
            <RowDefinition Height="*" />
        </Grid.RowDefinitions>
        <StackPanel Grid.Row="0" Orientation="Horizontal">
            <Button Click="addButton_Click">Add</Button>
            <Button Click="removeButton_Click">Remove</Button>
        </StackPanel>
        <Canvas Grid.Row="1" Name="baseCanvas">
            <Canvas Name="innerCanvas1" Height="30" Width="40" Top="20" Left="20" Background="Black">
                <TextBlock Foreground="White">装飾</TextBlock>
            </Canvas>
        </Canvas>
    </Grid>
</Window>

MainWindow.xaml.cs

using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;
using System.Windows.Shapes;

namespace WpfApplication4
{
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        private void addButton_Click(object sender, RoutedEventArgs e)
        {
            if (this.baseCanvas.Children.Count == 1)
            {
                Rectangle rect = new Rectangle();
                rect.Width = this.innerCanvas1.DesiredSize.Width;
                rect.Height = this.innerCanvas1.DesiredSize.Height;
                Canvas.SetTop(rect, 50);
                Canvas.SetLeft(rect, 100);
                VisualBrush brush = new VisualBrush(this.innerCanvas1);
                brush.Opacity = 0.3;
                rect.Fill = brush;
                this.baseCanvas.Children.Add(rect);
            }
        }

        private void removeButton_Click(object sender, RoutedEventArgs e)
        {
            if (this.baseCanvas.Children.Count > 1)
            {
                this.baseCanvas.Children.RemoveAt(1);
            }
        }
    }
}