Zoom Calculations

Hi all,

I'm trying to implement zooming on my page.  I would like the center to be wherever the mouse pointer currently is.  Not seeing the solution, but I know it has to do with the ratios in terms of screen coords and real coords.

Explinations would be extremely helpful.

XAML below, code is code behind.




XAML:
<UserControl x:Class="FloorPlan.Page"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
     MouseMove="Page_MouseMove">
    <UserControl.Resources>

        <Storyboard x:Name="ZoomStoryboard">
       


       
            <DoubleAnimation x:Name="ZoomAnimationX"
                                 Storyboard.TargetName="FloorScale"
                                 Storyboard.TargetProperty="ScaleX"
                                 Duration="0:0:0.2"/>
                                 
            <DoubleAnimation x:Name="ZoomAnimationY"
                                 Storyboard.TargetName="FloorScale"
                                 Storyboard.TargetProperty="ScaleY"
                                 Duration="0:0:0.2"/>



            <DoubleAnimation x:Name="CenterAnimationX"
                                 Storyboard.TargetName="FloorScale"
                                 Storyboard.TargetProperty="CenterX"
                                 Duration="0:0:0.2"/>

            <DoubleAnimation x:Name="CenterAnimationY"
                                 Storyboard.TargetName="FloorScale"
                                 Storyboard.TargetProperty="CenterY"
                                 Duration="0:0:0.2"/>
        </Storyboard>
     </UserControl.Resources>


    <Canvas x:Name="Floor" MouseWheel="Floor_MouseWheel">
        <Canvas.RenderTransform>
            <ScaleTransform x:Name="FloorScale" ScaleX="1" ScaleY="1"/>
        </Canvas.RenderTransform>        
       
        <Grid  ShowGridLines="false"  x:Name="LayoutRoot" Background="White"  >
       
        </Grid>
       
        <TextBlock x:Name="tbMouseX" Canvas.Left="100" Canvas.Top="100">
        </TextBlock>

        <TextBlock x:Name="tbMouseY" Canvas.Left="150" Canvas.Top="100">
        </TextBlock>
    </Canvas>
   
   
       
</UserControl>

Private Sub Floor_MouseWheel(ByVal sender As System.Object, ByVal e As System.Windows.Input.MouseWheelEventArgs)
        Static _ZoomSteps As Integer = 0
        Static _Zoom As Double = 0
        Static _CenterX As Double
        Static _CenterY As Double

        Dim deltaZoom As Double = e.Delta
 

        _Zoom += deltaZoom / 150
        If _Zoom <= 1 Then
            _Zoom = 1
        End If

        If deltaZoom >= 0 Then
            If _ZoomSteps = -1 Then
                _CenterX = 0
                _CenterY = 0
                _ZoomSteps = 0
            Else
                _CenterX = (_CenterX * (Math.Abs(_ZoomSteps) + mouseX) / (Math.Abs(_ZoomSteps + 1)))
                _CenterY = (_CenterY * (Math.Abs(_ZoomSteps) + mouseY) / (Math.Abs(_ZoomSteps + 1)))

                _ZoomSteps += 1
            End If
        Else
            If _ZoomSteps = 1 Then
                _CenterX = 0
                _CenterY = 0
                _ZoomSteps = 0
            Else
                _CenterX = (_CenterX * Math.Abs(_ZoomSteps) - mouseX) / (Math.Abs(_ZoomSteps - 1))
                _CenterY = (_CenterY * Math.Abs(_ZoomSteps) - mouseY) / (Math.Abs(_ZoomSteps - 1))
                _ZoomSteps -= 1
            End If
        End If



        ZoomAnimationX.[To] = _Zoom
        ZoomAnimationY.[To] = _Zoom

        CenterAnimationX.To = Math.Abs(_CenterX)
        CenterAnimationY.To = Math.Abs(_CenterY)


        ZoomStoryboard.Begin()
        mouseX = CType(_CenterX, Integer)
        mouseY = CType(_CenterY, Integer)
        tbMouseX.Text = mouseX.ToString()
        tbMouseY.Text = mouseY.ToString()
    End Sub

    Private Sub Page_MouseMove(ByVal sender As System.Object, ByVal e As System.Windows.Input.MouseEventArgs)

        mouseX = e.GetPosition(Nothing).X
        mouseY = e.GetPosition(Nothing).Y
        tbMouseX.Text = mouseX.ToString()
        tbMouseY.Text = mouseY.ToString()

    End Sub

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