title: InkCanvas saving produces the wrong dimensions
body: <p>I use a canvas that has a set width and height. It is 500x500 big and I also want to save it as such with this method:</p>
  
  <pre><code>    private async void SaveasGIF(object sender, RoutedEventArgs e)
      {
          var savePicker = new Windows.Storage.Pickers.FileSavePicker();
          savePicker.SuggestedStartLocation = Windows.Storage.Pickers.PickerLocationId.PicturesLibrary;
          savePicker.FileTypeChoices.Add("Gif with embedded ISF", new[] { ".gif" });
  
          Windows.Storage.StorageFile file = await savePicker.PickSaveFileAsync();
          if (null != file)
          {
              try
              {
                  using (Windows.Storage.Streams.IRandomAccessStream stream = await file.OpenAsync(Windows.Storage.FileAccessMode.ReadWrite))
                  {
                      // Truncate any existing stream in case the new file
                      // is smaller than the old file.
                      stream.Size = 0;
  
                      await MyInkCanvas.InkPresenter.StrokeContainer.SaveAsync(stream);
                  }
                  //MainPage.NotifyUser("File has been saved!", NotifyType.StatusMessage);
              }
              catch (Exception ex)
              {
                  //MainPage.NotifyUser(ex.Message, NotifyType.ErrorMessage);
              }
          }
          SaveGIF.IsChecked = false;
      }
  </code></pre>
  
  <p>But when I do so, the finished .gif file is cropped and has dimensions like 421x643. </p>
  
  <p>What can I change to fix this?</p>