public void saveInkPresenter()
{
Rect rect = new Rect(0, 0, 300, 300);
RenderTargetBitmap targetBitmap = new RenderTargetBitmap((int)rect.Right, (int)rect.Bottom, 96d, 96d, PixelFormats.Default);
ink.Measure(new Size((int)rect.Right, (int)rect.Bottom));
ink.Arrange(new Rect(new Size((int)rect.Right, (int)rect.Bottom)));
targetBitmap.Render(ink);
targetBitmap.Freeze();
PngBitmapEncoder png = new PngBitmapEncoder();
png.Frames.Add(BitmapFrame.Create(targetBitmap));
using (Stream stm = File.Create("test.png"))
{
png.Save(stm);
}
}