Silveright ScrollViewer with Image and ScaleTransform

I have the following xaml.

<ScrollViewer HorizontalAlignment="Stretch" Margin="107,0,0,0" Name="scrollViewer1" VerticalAlignment="Stretch" HorizontalScrollBarVisibility="Visible">
    <Image Name="image1" Stretch="None" MouseWheel="image1_MouseWheel" RenderTransformOrigin="0,0">
    </Image>
</ScrollViewer>

An the following code behind.

// initialise.
private TransformGroup group = new TransformGroup();
private ScaleTransform st = new ScaleTransform();
group.Children.Add(st);
image1.RenderTransform = group

// mouse event.
TransformGroup group = (TransformGroup)image1.RenderTransform;
ScaleTransform scale = (ScaleTransform)group.Children.Last();
double zoom = e.Delta > 0 ? .2 : -.2;
scale.ScaleX += zoom;开发者_如何学Go
scale.ScaleY += zoom;

How do I get the scroller to take into account that the image is now a different size. The scroll bars remain the same size, and I cannot work out how to change them.

Thanks

You need the LayoutTransformer from the Silverlight Toolkit. Instead of setting a RenderTransform on your Image, put it inside a LayoutTransformer.

have you tried calling InvalidateScrollInfo on the scrollviewer?