.net 8 wpf

My requirement is to merge and print engineering drawings

My drawings are SolidWorks drawings

I first converted the drawings into PDF format

Then each page of the PDF was converted into an image

Then, the image was loaded using WrapPanel

Finally, use the RenderTargetBitmap virtual rendering to save the image

The lower part of the exported JPG file is grayed out,

And the Border rendered correctly, but the Image content inside the Border is grayed out

At first, I thought it might be because some content was not displayed using ScrollViewer, and there were some optimization mechanisms in WPF

As a result, I directly placed the content of RenderTarget bitmap on the Source of Image, and the result is like this

right site is a Image Control ，ImageSource is the WrapPanel visual render

this is picture attr

this is error part in picture

another error part in picture file ,but zhe Border Posion is Right

public static ImageSource ElementToBitmap(FrameworkElement element, Stream stream, BitmapEncoder? encoder = null)
{
    encoder = encoder ?? new JpegBitmapEncoder() { QualityLevel = 100 };
    var renderBitmap = new RenderTargetBitmap((int)element.ActualWidth, (int)element.ActualHeight, 96, 96, PixelFormats.Pbgra32);
    renderBitmap.Render(element);
    encoder.Frames.Add(BitmapFrame.Create(renderBitmap));
    encoder.Save(stream);
    return renderBitmap;
}
private void OutPut_Click(object sender, RoutedEventArgs e)
{
    var saveFileDialog = new SaveFileDialog()
    {
        Filter = "Image files (*.jpg)|*.jpg"
    };
    if(saveFileDialog.ShowDialog() != true) return;
    Task.Run(() => {
        App.UIDispatcher.Invoke(() => {
            using (var stream = saveFileDialog.OpenFile())
            {
                var source = SolidWorkManager.ElementToBitmap(RangePanel, stream);
                TestImage.Source = source;
            }
        });
    });
}

<Border  Grid.Column="1" Width="900" CornerRadius="5" BorderBrush="Black" BorderThickness="2" Margin="0,0,0,20">
    <ScrollViewer VerticalAlignment="Top" >
        <Viewbox Width="880" Height="Auto">
            <WrapPanel x:Name="RangePanel" Width="{Binding RealWidth}" Height="Auto" Margin="{Binding RangeMargin}" Background="White">
                <ItemsControl ItemsSource="{Binding PicMergeItems}" Visibility="Visible">
                    <ItemsControl.ItemTemplate>
                        <DataTemplate>
                            <Border Visibility="Visible" Margin="{Binding ItemMargin}" VerticalAlignment="Top" BorderBrush="Black" BorderThickness="1" Padding="0">
                                <Image Visibility="Visible" Tag="{Binding}" Source="{Binding FullPath}" Width="{Binding Width}" Height="{Binding Height}" MouseDown="Image_MouseDown">
                                    <Image.LayoutTransform>
                                        <RotateTransform Angle="{Binding Angle}" />
                                    </Image.LayoutTransform>
                                </Image>
                            </Border>
                        </DataTemplate>
                    </ItemsControl.ItemTemplate>
                    <ItemsControl.ItemsPanel>
                        <ItemsPanelTemplate>
                            <WrapPanel Visibility="Visible"/>
                        </ItemsPanelTemplate>
                    </ItemsControl.ItemsPanel>
                </ItemsControl>
            </WrapPanel>
        </Viewbox>
    </ScrollViewer>
</Border>