This page contains a <canvas>. A mathematical
      equation is inserted at the center using the following code:
  var image =
    TeXZilla.toImage("\\vec{F} = G \\frac{m_1 m_2}{r^2} \\mathbf{u}");
  image. {
    context.drawImage(image,
                      (canvas.width - image.width) / 2,
                      (canvas.height - image.height) / 2);