WPF performance on scaling a large scene

Question

I have a full screen app that I want to be able to zoom in on certain areas.

I have the code working fine, but I notice that when I get closer in, the zoom in animation (which animates the ScaleTransform.ScaleX and ScaleTransform.ScaleY properties on a Parent canvas) starts to jerk down a little and the frame rate suffers.

Im not using any BitmapEffects or anything, and ideally I would like my scene to get more complicated than it currently already is.

The scene is quite large, 1980x1024, this is a requirement and cannot be changed.

The current layout is like this:

<Canvas x:name="LayoutRoot">
  <Canvas x:Name="ContainerCanvas">
    <local:MyControl x:Name="c1" />
    <!-- numerous or ther controls and elements that compose the scene  -->
  </Canvas>
</Canvas>

The code that zooms in just animates the RenderTransform of the ContainerCanvas, which in tern, scales its children which gives the desired effect.

However, Im wondering if I need to swap out the ContainerCanvas for a ViewBox or something like that? Ive never really worked with ViewBox/Viewport controls before in WPF can they even help me out here?

Smooth zooming is a huge requirement of the client and I must get this resolved.

All ideas are welcome

Thanks a lot

Mark

Answer 1

I have a similar problem with bitonal images which need to be zoomed and smooth panned, but being bitonal need to be anti-aliased to make onscreen viewing acceptable. Obviously this anti-aliasing can cause performance issues. Have you played around with the RenderOptions.SetBitmapScalingMode() for the image object your are displaying? If so you may have to trade off between the speed/performance of the zoom animation and the quality of the rendered image.

One possible solution I had thought of, but have not yet had time to implement, would be to switch into a low quality bitmap scaling mode during the animation, and switching back to high quality at the end of the animation.