Resize of Big images within a viewbox

[sehnkim]

Hi, Experts.

I am dealing with 5 big images. (The resolution is about 5000 * 3000).
After loading the images and displaying them on the same canvas, I zoom-in and zoom-out the images at the same time by moving a slider.
But during this zoom-in/out actions, my program (actually my computer) is frozen.
When I used 10 small images (about 800 * 600), there was no problem.

The following code is called when I change the image size (by zoom-in/out).

private static void OnImageZoomChanged(DependencyObject obj, DependencyPropertyChangedEventArgs args) 
{ 
    ImageScrollControl control = obj as ImageScrollControl; 
    double zoom = (double)args.NewValue; 
 
    if (control == null || zoom < 0.1 || zoom > 21) return; 
 
    else 
    { 
        // double scale = (zoom <= 20) ? (zoom / 20) : (zoom - 19); 
        control.ImageViewBox.Height = control._pixelHeight * zoom; 
        control.ImageViewBox.Width = control._pixelWidth * zoom; 
                         
        control.ImageScrollViewer.UpdateLayout(); 
    } 
}

If I comment out the following two lines, then works fine.
// control.ImageViewBox.Height = control._pixelHeight * zoom;
// control.ImageViewBox.Width = control._pixelWidth * zoom;
But the size of the image in the viewbox doesn't change at all.

The following is the XAML code.

<TabControl Height="Auto" 
            Width="Auto" 
            x:Name="LogTabControl"> 
    <TabItem Header="Image"> 
        <RegistrationFront_UI_Custom:ZoomNMoveScrollControl  
                      x:Name="ImageScrollViewer" 
                      Width="Auto" 
                      Height="Auto" 
                      HorizontalContentAlignment="Center" 
                      VerticalContentAlignment="Center" 
                      HorizontalScrollBarVisibility="Auto" 
                      VerticalScrollBarVisibility="Auto" 
                      PreviewMouseWheel="ImageScrollViewer_PreviewMouseWheel"> 
            <Viewbox x:Name="ImageViewBox" 
                     OpacityMask="{x:Null}" 
                     ScrollViewer.HorizontalScrollBarVisibility="Disabled"> 
                <Canvas x:Name="ImageCanvas" 
                        HorizontalAlignment="Center" 
                        VerticalAlignment="Center">                  
                     
                </Canvas> 
            </Viewbox> 
        </RegistrationFront_UI_Custom:ZoomNMoveScrollControl> 
    </TabItem> 
    <TabItem  
             x:Name="LogTab" 
             Header="Logs" 
             Width="Auto" 
             Height="Auto"> 
        <RegistrationFront_UI_Custom:LogBrowser 
          x:Name="LogBrowserTab" 
          CurrentProject="{Binding Path=CurrentProject, ElementName=UserControl, Mode=Default}" /> 
    </TabItem> 
</TabControl>

Do you have any idea about this problem?
Any comment will be really appreciated.

Thank you.

Kim.