如何在WPF中制作UIElement的屏幕截图

我在创建 scatterview 的屏幕截图时遇到问题。我的屏幕截图总是包含黑框。

这是我的 XAML 代码：

<s:SurfaceWindow
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:s="http://schemas.microsoft.com/surface/2008"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" mc:Ignorable="d" x:Class="MakeScreenshots.SurfaceWindow1"
    Title="MakeScreenshots" Width="1000" Height="700"
    >
  <s:SurfaceWindow.Resources>
    <ImageBrush x:Key="WindowBackground" Stretch="None" Opacity="0.6" ImageSource="pack://application:,,,/Resources/WindowBackground.jpg"/>
  </s:SurfaceWindow.Resources>

  <Grid x:Name="GlobalGrid" Background="{StaticResource WindowBackground}" Width="1000" Height="700" >

    <s:ScatterView x:Name="ScatterViewScreenShot" Margin="108,89,176,73" Width="700" Height="500">
        <s:ScatterView.Background>
            <SolidColorBrush Color="{DynamicResource {x:Static SystemColors.ActiveCaptionColorKey}}"/>
        </s:ScatterView.Background>
        <s:ScatterViewItem Margin="0,-26.953,-130.946,-23.047" Content="ScatterViewItem 3" HorizontalAlignment="Right" Width="125.826"/>
        <s:ScatterViewItem Margin="0,0,-490.513,-151.256" HorizontalAlignment="Right" Width="125.77" Height="60.427" VerticalAlignment="Bottom" Content="ScatterViewItem 2"/>
        <s:ScatterViewItem Content="ScatterViewItem 1" Margin="-331.43,0,0,-129.589" HorizontalAlignment="Left" Width="177.949" Height="67.905" VerticalAlignment="Bottom"/>
    </s:ScatterView>
    <Button x:Name="MakeScreenShotButton" Click="MakeScreenShotButton_Click" Content="MakeScreenShot" Margin="267,17,343,0" VerticalAlignment="Top" Height="38.96"/>
        <Button Content="MakeScreenShotButton2" Height="39" HorizontalAlignment="Left" Margin="116,614,0,0" Name="button1" VerticalAlignment="Top" Width="301" Click="MakeScreenShotButton2_Click" />
        <Button Content="MakeScreenShotButton3"  Click="MakeScreenShotButton3_Click" Height="39" HorizontalAlignment="Left" Margin="822,207,0,0" Name="button2" VerticalAlignment="Top" Width="147" />
        <Button Content="MakeScreenShotButton4" Click="MakeScreenShotButton4_Click" Height="39" HorizontalAlignment="Left" Margin="822,349,0,0" Name="button3" VerticalAlignment="Top" Width="147" />
        <Button Content="MakeScreenShotButton5" Click="MakeScreenShotButton5_Click" Height="39" HorizontalAlignment="Left" Margin="822,443,0,0" Name="button4" VerticalAlignment="Top" Width="147" />
    </Grid>
</s:SurfaceWindow>

这是 C# 代码：

    private void MakeScreenShotButton_Click(object sender, RoutedEventArgs e)
    {          
        RenderTargetBitmap targetBitmap = new RenderTargetBitmap((int)ScatterViewScreenShot.ActualWidth, (int)ScatterViewScreenShot.ActualHeight, 80d, 80d, PixelFormats.Default);

        targetBitmap.Render(ScatterViewScreenShot);

        // add the RenderTargetBitmap to a Bitmapencoder

        JpegBitmapEncoder encoder = new JpegBitmapEncoder();
        encoder.Frames.Add(BitmapFrame.Create(targetBitmap));

        // Encoder zum Speichern des Bildes
        JpegBitmapEncoder encoderToSave = new JpegBitmapEncoder();
        encoderToSave.Frames.Add(BitmapFrame.Create(targetBitmap));

        // Speichern des Bildes auf der Festplatte
        string fileName = "M:\\TestForStackOverflow.jpg";
        System.IO.FileStream fs = System.IO.File.Open(fileName, System.IO.FileMode.OpenOrCreate);
        encoderToSave.Save(fs);

        encoder.QualityLevel = 40;

        MemoryStream ms = new MemoryStream();
        encoder.Save(ms);

        // Convert Image to byte[]
        byte[] imageBytes = ms.ToArray();

        int anzahlBytes = imageBytes.Length;

        string imageAsBase64String = Convert.ToBase64String(imageBytes);

        TCP_Client client = new TCP_Client("192.168.5.3", 4321);
        client.sendeNachricht(imageAsBase64String);
    }

    private void MakeScreenShotButton2_Click(object sender, RoutedEventArgs e)
    {
        // 1. Bitmap der gewünschten Größe erstellen
        int width = (int)ScatterViewScreenShot.ActualWidth;
        int height = (int)ScatterViewScreenShot.ActualHeight;
        RenderTargetBitmap rtb = new RenderTargetBitmap(width, height, 100d, 100d, PixelFormats.Default); // 500 x 500 genau wie bei den Produktfotos

        // 2. Control in Bitmap hinein rendern
        Visual vis = (Visual)ScatterViewScreenShot;
        rtb.Render(vis);

        // 3. Control-Image erzeugen und dem Control-Image als Source das Bitmap übergeben
        System.Windows.Controls.Image img = new System.Windows.Controls.Image();
        img.Source = rtb;
        img.Stretch = Stretch.None;

        // 4. Aktualisieren der Größe des Elements entsprechend des Inhaltes mittels der Methoden Measure und Arrange.
        img.Measure(new System.Windows.Size(width, height));
        System.Windows.Size sizeImage = img.DesiredSize;
        img.Arrange(new System.Windows.Rect(new System.Windows.Point(0, 0), sizeImage));

        // 5. Image wird mit der korrekten Größe erneut gerendert und an PngBitmapEncoder übergeben
        RenderTargetBitmap rtb2 = new RenderTargetBitmap((int)rtb.Width, (int)rtb.Height, 60, 60, PixelFormats.Default);
        rtb2.Render(img);

        PngBitmapEncoder jpeg = new PngBitmapEncoder();
        jpeg.Frames.Add(BitmapFrame.Create(rtb2));


        // 6. Image in Stream schreiben
        MemoryStream ms = new MemoryStream();
        jpeg.Save(ms);

        // Convert Image to byte[]
        byte[] imageBytes = ms.ToArray();

        int anzahlBytes = imageBytes.Length;

        string imageAsBase64String = Convert.ToBase64String(imageBytes);

        TCP_Client client = new TCP_Client("192.168.5.3", 4321);
        client.sendeNachricht(imageAsBase64String);
    }

    private void MakeScreenShotButton3_Click(object sender, RoutedEventArgs e)
    {
        int width_x = 240;
        int width_y = 400;

        Bitmap screen = TakeScreenshot(100, 100, width_x, width_y);

        System.Drawing.Image img = (System.Drawing.Image)screen;
        //Image img = Image.FromFile("bla.jpg");
        MemoryStream ms = new MemoryStream();

        try
        {
            //Ein ImageCodecInfo-Objekt für den JPEG-Codec anlegen
            ImageCodecInfo jpegCodec = null;

            //Den Qualitätsarameter konfigurieren (Qualitätsfaktor in
            //Prozent angeben)

            EncoderParameter qualitaetsParameter = new EncoderParameter(
                        System.Drawing.Imaging.Encoder.Quality, 40);

            //Alle im System verfügbaren Codecs auflisten
            ImageCodecInfo[] alleCodecs = ImageCodecInfo.GetImageEncoders();

            EncoderParameters codecParameter = new EncoderParameters(1);
            codecParameter.Param[0] = qualitaetsParameter;

            //Den JPEG-Codec unter allen Codecs finden und dem
            //Codec-Info-Objekt zuweisen
            for (int i = 0; i < alleCodecs.Length; i++)
            {
                if (alleCodecs[i].MimeType == "image/jpeg")
                {
                    jpegCodec = alleCodecs[i];
                    break;
                }
            }

            // Bild in Stream schreiben
            img.Save(ms, jpegCodec, codecParameter);
        }
        catch (ArgumentException w)
        {
            throw w;
        }

        //  Console.WriteLine(StreamToBase64(ms, System.Drawing.Imaging.ImageFormat.Jpeg));
        String bildBase64 = StreamToBase64(ms, System.Drawing.Imaging.ImageFormat.Jpeg);

        TCP_Client client = new TCP_Client("192.168.5.3", 4321);
        client.sendeNachricht(bildBase64);
    }

    private void MakeScreenShotButton4_Click(object sender, RoutedEventArgs e)
    {
        // save current canvas transform
        Transform transform = ScatterViewScreenShot.LayoutTransform;

        // get size of control
        System.Windows.Size sizeOfControl = new System.Windows.Size(ScatterViewScreenShot.ActualWidth, ScatterViewScreenShot.ActualHeight);
        // measure and arrange the control
        ScatterViewScreenShot.Measure(sizeOfControl);
        // arrange the surface
        ScatterViewScreenShot.Arrange(new Rect(sizeOfControl));

        // craete and render surface and push bitmap to it
        RenderTargetBitmap renderBitmap = new RenderTargetBitmap((Int32)sizeOfControl.Width, (Int32)sizeOfControl.Height, 96d, 96d, PixelFormats.Pbgra32);
        // now render surface to bitmap
        renderBitmap.Render(ScatterViewScreenShot);

        // encode png data
        PngBitmapEncoder pngEncoder = new PngBitmapEncoder();
        // puch rendered bitmap into it
        pngEncoder.Frames.Add(BitmapFrame.Create(renderBitmap));

        /* Speichern des Bildes auf der Festplatte
        string fileName = "M:\\ScreenshotClick4.jpg";
        System.IO.FileStream fs = System.IO.File.Open(fileName, System.IO.FileMode.OpenOrCreate);
        pngEncoder.Save(fs);*/

        // Encoder zum Senden des Bildes
        JpegBitmapEncoder encoder = new JpegBitmapEncoder();
        encoder.Frames.Add(BitmapFrame.Create(renderBitmap));

        MemoryStream ms = new MemoryStream();
        encoder.Save(ms);

        // Convert Image to byte[]
        byte[] imageBytes = ms.ToArray();

        int anzahlBytes = imageBytes.Length;

        string imageAsBase64String = Convert.ToBase64String(imageBytes);

        TCP_Client client = new TCP_Client("192.168.5.3", 4321);
        client.sendeNachricht(imageAsBase64String);

    }

    private void MakeScreenShotButton5_Click(object sender, RoutedEventArgs e)
    {
        int scale = 1;

        double actualHeight = ScatterViewScreenShot.RenderSize.Height;
        double actualWidth = ScatterViewScreenShot.RenderSize.Width;

        double renderHeight = actualHeight * scale;
        double renderWidth = actualWidth * scale;

        RenderTargetBitmap renderTarget = new RenderTargetBitmap((int)renderWidth, (int)renderHeight, 96, 96, PixelFormats.Pbgra32);
        VisualBrush sourceBrush = new VisualBrush(ScatterViewScreenShot);

        DrawingVisual drawingVisual = new DrawingVisual();
        DrawingContext drawingContext = drawingVisual.RenderOpen();

        using (drawingContext)
        {
            drawingContext.PushTransform(new ScaleTransform(actualWidth, actualHeight));
            drawingContext.DrawRectangle(sourceBrush, null, new Rect(new System.Windows.Point(0, 0), new System.Windows.Point(actualWidth, actualHeight)));
        }
        renderTarget.Render(drawingVisual);

        JpegBitmapEncoder jpgEncoder = new JpegBitmapEncoder();
        jpgEncoder.QualityLevel = 40;
        jpgEncoder.Frames.Add(BitmapFrame.Create(renderTarget));

        MemoryStream ms = new MemoryStream();
        jpgEncoder.Save(ms);

        // Convert Image to byte[]
        byte[] imageBytes = ms.ToArray();

        int anzahlBytes = imageBytes.Length;

        string imageAsBase64String = Convert.ToBase64String(imageBytes);

        TCP_Client client = new TCP_Client("192.168.5.3", 4321);
        client.sendeNachricht(imageAsBase64String);

    }

    #region Hilfsmethoden

    public string StreamToBase64(MemoryStream ms, System.Drawing.Imaging.ImageFormat format)
    {
        // Convert Image to byte[]
        byte[] imageBytes = ms.ToArray();

        // Convert byte[] to Base64 String
        string base64String = Convert.ToBase64String(imageBytes);
        return base64String;
    }

    private Bitmap TakeScreenshot(int StartX, int StartY, int Width, int Height)
    {
        Bitmap Screenshot = new Bitmap(Width, Height);
        Graphics G = Graphics.FromImage(Screenshot);

        G.CopyFromScreen(StartX, StartY, 0, 0, new System.Drawing.Size(Width, Height), CopyPixelOperation.SourceCopy);
        return Screenshot;
    }

    #endregion


}
}

我发现以下文章可以解决您的问题： Take WPF “Screenshots” (Link https://www.grumpydev.com/2009/01/03/taking-wpf-screenshots/到博客文章）

///
/// Gets a JPG "screenshot" of the current UIElement
///
/// UIElement to screenshot
/// Scale to render the screenshot
/// JPG Quality
/// Byte array of JPG data
public static byte[] GetJpgImage(this UIElement source, double scale, int quality)
{
    double actualHeight = source.RenderSize.Height;
    double actualWidth = source.RenderSize.Width;

    double renderHeight = actualHeight * scale;
    double renderWidth = actualWidth * scale;

    RenderTargetBitmap renderTarget = new RenderTargetBitmap((int) renderWidth, (int) renderHeight, 96, 96, PixelFormats.Pbgra32);
    VisualBrush sourceBrush = new VisualBrush(source);

    DrawingVisual drawingVisual = new DrawingVisual();
    DrawingContext drawingContext = drawingVisual.RenderOpen();

    using (drawingContext)
    {
        drawingContext.PushTransform(new ScaleTransform(scale, scale));
        drawingContext.DrawRectangle(sourceBrush, null, new Rect(new Point(0, 0), new Point(actualWidth, actualHeight)));
    }
    renderTarget.Render(drawingVisual);

    JpegBitmapEncoder jpgEncoder = new JpegBitmapEncoder();
    jpgEncoder.QualityLevel = quality;
    jpgEncoder.Frames.Add(BitmapFrame.Create(renderTarget));

    Byte[] _imageArray;

    using (MemoryStream outputStream = new MemoryStream())
    {
        jpgEncoder.Save(outputStream);
        _imageArray = outputStream.ToArray();
    }

    return _imageArray;
}