How make a Screenshot of UIElement in WPF

Question

I have a problem with creating a screenshot of a scatterview. My screenshot always contains a black frame.

Here\'s my XAML-Code:

Answer 1

the following article has a workaround for your problem:

Taking WPF “Screenshots”

http://www.grumpydev.com/2009/01/03/taking-wpf-screenshots/

///
/// 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;
}

hope this helps

Answer 2

I found a quite simple way that works very well. Method TakeScreenshot makes a screenshot an returns it as a bitmap. MakeScreenShotButton_Click encodes the bitmap in jpeg, saves it, and sends it to the client as base64 String.

Here are the code snippets. First TakeScreenshot:

private Bitmap TakeScreenshot(int StartX, int StartY, int Width, int Height)
        {
            // Bitmap in right size
            Bitmap Screenshot = new Bitmap(Width, Height);
            Graphics G = Graphics.FromImage(Screenshot);
            // snip wanted area
            G.CopyFromScreen(StartX, StartY, 0, 0, new System.Drawing.Size(Width, Height), CopyPixelOperation.SourceCopy);

            // save uncompressed bitmap to disk
            string fileName = "C:\\TestBMP.bmp";
            System.IO.FileStream fs = System.IO.File.Open(fileName, System.IO.FileMode.OpenOrCreate);
            Screenshot.Save(fs, System.Drawing.Imaging.ImageFormat.Bmp);
            fs.Close();

            return Screenshot;
        }

And that's the MakeScreenShotButton_Click:

private void MakeScreenShotButton3_Click(object sender, RoutedEventArgs e)
    {
        // Start values
        System.Windows.Point absolutPosition = ScatterViewScreenShot.TranslatePoint(new System.Windows.Point(0, 0), sw1);
        System.Windows.Point screenPosition = this.PointToScreen(absolutPosition);

        // Catch width and hight of scatterview
        int widthScatterView = (int)ScatterViewScreenShot.ActualWidth;
        int heightScatterView = (int)ScatterViewScreenShot.ActualHeight;

        // Screenshot as bitmap TakeScreenshot(StartWert_X, StartWert_Y, BreiteBild, HöheBild)
        Bitmap screen = TakeScreenshot((int)screenPosition.X, (int)screenPosition.Y, widthScatterView, heightScatterView);

        MemoryStream ms = new MemoryStream();

        try
        {
            //ImageCodecInfo - Object
            ImageCodecInfo jpegCodec = null;

            // Quality-Parameter
            EncoderParameter qualitaetsParameter = new EncoderParameter(
                        System.Drawing.Imaging.Encoder.Quality, 40L);

            //Show available Codes in List
            ImageCodecInfo[] alleCodecs = ImageCodecInfo.GetImageEncoders();

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

            //Find Jpeg-Codec
            //Codec-Info-Object 
            for (int i = 0; i < alleCodecs.Length; i++)
            {
                if (alleCodecs[i].MimeType == "image/jpeg")
                {
                    jpegCodec = alleCodecs[i];
                    break;
                }
            }

            // save image in stream
            screen.Save(ms, jpegCodec, codecParameter);
        }
        catch (Exception k)
        {
            throw k;
        }

        // Convert image in Byte-Array 
        byte [] imageBytes = ms.ToArray();

        // Convert Byte-Array in Base64String --> Image as String
        string bildBase64 = Convert.ToBase64String(imageBytes);

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

It works without problems!

Cheers, Dennis