c# – 获取画布背景的图像画笔控件的实际大小

我试图弄清楚如何获得在Canvas控件上设置为背景的图像的“视图大小”.
背景设置为 ImageBrush,strech设置为UniForm.
如果strech属性设置为Fill,那么我可以使用画布的ActualWidth和ActualHeight.
这对UniForm来说是不可能的,所以我该如何处理呢？

这是我的XAML：

<Grid DataContext="{Binding ImageViewerVM.CurrentImage}">
    <controls:RubberBandingCanvas x:Name="RubCanvas">
        <controls:RubberBandingCanvas.Resources>
            <Converters:ControlVisibilityConverter x:Key="VisibilityHiddenConverter" />
            <Converters:StringToBitmapConverter x:Key="StringToBitmapConverter" />
        </controls:RubberBandingCanvas.Resources>
        <controls:RubberBandingCanvas.Background>
            <ImageBrush x:Name="ibCurrentImage" ImageSource="{Binding Path=Path,Converter={StaticResource StringToBitmapConverter}}" Stretch="Uniform"></ImageBrush>
        </controls:RubberBandingCanvas.Background>
        <Ellipse Canvas.Top="10" Canvas.Right="10" Fill="Red" Stroke="Black" Height="15" Width="15" Visibility="{Binding Path=IsMultiTiff,Converter={StaticResource VisibilityHiddenConverter}}"/>            
    </controls:RubberBandingCanvas>
</Grid>

最好的祝福,
杰斯珀詹森

var ratio = Math.Min(RubCanvas.RenderSize.Width / CanvasBackground.ImageSource.Width,RubCanvas.RenderSize.Height / CanvasBackground.ImageSource.Height);
var imageBrushWidth = CanvasBackground.ImageSource.Width * ratio;
var imageBrushHeight = CanvasBackground.ImageSource.Height * ratio;