dozob

var rtbmp = new RenderTargetBitmap(
    (int)myCanvas.ActualWidth,
    (int)myCanvas.ActualHeight,
    96d, 96d,
    PixelFormats.Default);

rtbmp.Render(myCanvas);

using (var fs = new FileStream(sFilePath, FileMode.Create, FileAccess.Write, FileShare.None))
{
    var encoder = new JpegBitmapEncoder();
    encoder.Frames.Add(BitmapFrame.Create(rtbmp));
    encoder.Save(fs);
}