CODEWITHSUNDEEP
c#wpfpngwpftoolkitmschart
VilemRousi
VilemRousi

Reputation: 2142

How to export chart from WPF Toolkit (MS Chart) to PNG. It doesn't work, it creates only a black PNG

I cannot export MS Chart (from WPF toolkit) to PNG. I following step from different forums, but after everything, my PNG is completely black. What am I doing wrong?

private void export_graf_Click(object sender, RoutedEventArgs e)
        {
            if (mcChart.Series[0] == null)
            {
                MessageBox.Show("there is nothing to export");
            }
            else
            {

           RenderTargetBitmap renderBitmap = new RenderTargetBitmap((int)mcChart.ActualWidth,    (int)mcChart.ActualHeight, 95d, 95d, PixelFormats.Pbgra32);


                renderBitmap.Render(mcChart);

                Microsoft.Win32.SaveFileDialog uloz_obr = new Microsoft.Win32.SaveFileDialog();
                uloz_obr.FileName = "Graf";
                uloz_obr.DefaultExt = "png";


                Nullable<bool> result = uloz_obr.ShowDialog();
                if (result == true)
                {
                    string obr_cesta = uloz_obr.FileName; //cesta k souboru

              using (FileStream outStream = new FileStream(obr_cesta, FileMode.Create))
                    {
                        PngBitmapEncoder encoder = new PngBitmapEncoder();
                        encoder.Frames.Add(BitmapFrame.Create(renderBitmap));
                        encoder.Save(outStream);
                    }

                }

Upvotes: 0

Views: 2050

Answers (1)

Scott
Scott

Reputation: 1876

I think you are encountering a layout issue. The RenderTargetBitmap class works on the visual layer, which includes offsets and transforms inherited from its visual parents. You should isolate the visual element when rendering it to a BitmapFrame. You can also specify a background color without affecting your window's visual tree, unless you want a transparent background. The PNG format supports alpha transparency and some image viewers display transparent pixels as black.

The default dpi for WPF is 96. I'm not sure why you specified 95. This isn't a zero bound index or anything like that. The sample below uses 96dpi.

private void export_graf_Click(object sender, RoutedEventArgs e)
{
    if (mcChart.Series[0] == null)
    {
        MessageBox.Show("there is nothing to export");
    }
    else
    {
        Rect bounds = VisualTreeHelper.GetDescendantBounds(mcChart);

        RenderTargetBitmap renderBitmap = new RenderTargetBitmap((int)bounds.Width, (int)bounds.Height, 96, 96, PixelFormats.Pbgra32);

        DrawingVisual isolatedVisual = new DrawingVisual();
        using (DrawingContext drawing = isolatedVisual.RenderOpen())
        {
            drawing.DrawRectangle(Brushes.White, null, new Rect(new Point(), bounds.Size)); // Optional Background
            drawing.DrawRectangle(new VisualBrush(mcChart), null, new Rect(new Point(), bounds.Size));
        }

        renderBitmap.Render(isolatedVisual);

        Microsoft.Win32.SaveFileDialog uloz_obr = new Microsoft.Win32.SaveFileDialog();
        uloz_obr.FileName = "Graf";
        uloz_obr.DefaultExt = "png";

        Nullable<bool> result = uloz_obr.ShowDialog();
        if (result == true)
        {
            string obr_cesta = uloz_obr.FileName;

            using (FileStream outStream = new FileStream(obr_cesta, FileMode.Create))
            {
                PngBitmapEncoder encoder = new PngBitmapEncoder();
                encoder.Frames.Add(BitmapFrame.Create(renderBitmap));
                encoder.Save(outStream);
            }
        }
    }
}

Upvotes: 3

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