title: Set background color in Bitmap Image
body: <p>I want to save my canvas to image. It works but background color is black. How I must add to change the color? </p>
  
  <p>I use this code:</p>
  
  <pre><code>Size size = new Size(surface.Width, surface.Height);
  
  surface.Measure(size);
  surface.Arrange(new Rect(size));
  
  // Create a render bitmap and push the surface to it
  RenderTargetBitmap renderBitmap =
      new RenderTargetBitmap((int)size.Width, (int)size.Height, 96d, 96d,
                             PixelFormats.Pbgra32);
  renderBitmap.Render(surface);
  
  // Create a file stream for saving image
  using (FileStream outStream = new FileStream(filename, FileMode.Create))
  {
      BmpBitmapEncoder encoder = new BmpBitmapEncoder();
      // push the rendered bitmap to it
      encoder.Frames.Add(BitmapFrame.Create(renderBitmap));
      // save the data to the stream
      encoder.Save(outStream);
  }
  </code></pre>