You could use the project from the link you posted and then use the
method to create a bitmap. This bitmap can then be saved as*.bmp, *.jpg...
here is an example:
private void toolStripButtonSave_Click(object sender, EventArgs e)
int w = drawArea.Width;
int h = drawArea.Height;
Bitmap bmp = new Bitmap(w, h);
drawArea.DrawToBitmap(bmp, Rectangle.FromLTRB(0, 0, w, h));
As you can see I modified the event handler for the "Save" toolbar button. I have tested it and it works fine!