Замена Graphics.DrawLine на DrawingContext.DrawLine

Имеется код, который нормально работает в WinForms, но хочется перенести его в WPF.

static class GraphicsExtension
{
  private static void DrawCubicCurve(this Graphics graphics, Pen pen, float beta, float step, PointF start, PointF end, float a3, float a2, float a1, float a0, float b3, float b2, float b1, float b0)
  {
    float xPrev, yPrev;
    float xNext, yNext;
    bool stop = false;
    xPrev = beta * a0 + (1 - beta) * start.X;
    yPrev = beta * b0 + (1 - beta) * start.Y;
    for (float t = step; ; t += step)
    {
      if (stop)
        break;
      if (t >= 1)
      {
        stop = true;
        t = 1;
      }
      xNext = beta * (a3 * t * t * t + a2 * t * t + a1 * t + a0) + (1 - beta) * (start.X + (end.X - start.X) * t);
      yNext = beta * (b3 * t * t * t + b2 * t * t + b1 * t + b0) + (1 - beta) * (start.Y + (end.Y - start.Y) * t);
      graphics.DrawLine(pen, xPrev, yPrev, xNext, yNext);
      xPrev = xNext;
      yPrev = yNext;
    }
  }
  internal static void DrawBSpline(this Graphics graphics, Pen pen, PointF[] points, float beta, float step)
  {
    if (points == null)
      throw new ArgumentNullException("The point array must not be null.");
    if (beta < 0 || beta > 1)
      throw new ArgumentException("The bundling strength must be >= 0 and <= 1.");
    if (step <= 0 || step > 1)
      throw new ArgumentException("The step must be > 0 and <= 1.");
    if (points.Length <= 1)
      return;
    if (points.Length == 2)
    {
      graphics.DrawLine(pen, points[0], points[1]);
      return;
    }
    float a3, a2, a1, a0, b3, b2, b1, b0;
    float deltaX = (points[points.Length - 1].X - points[0].X) / (points.Length - 1);
    float deltaY = (points[points.Length - 1].Y - points[0].Y) / (points.Length - 1);
    PointF start, end;
    {
      a0 = points[0].X;
      b0 = points[0].Y;
      a1 = points[1].X - points[0].X;
      b1 = points[1].Y - points[0].Y;
      a2 = 0;
      b2 = 0;
      a3 = (points[0].X - 2 * points[1].X + points[2].X) / 6;
      b3 = (points[0].Y - 2 * points[1].Y + points[2].Y) / 6;
      start = points[0];
      end = new PointF
      (
        points[0].X + deltaX,
        points[0].Y + deltaY
      );
      graphics.DrawCubicCurve(pen, beta, step, start, end, a3, a2, a1, a0, b3, b2, b1, b0);
    }
    for (int i = 1; i < points.Length - 2; i++)
    {
      a0 = (points[i - 1].X + 4 * points[i].X + points[i + 1].X) / 6;
      b0 = (points[i - 1].Y + 4 * points[i].Y + points[i + 1].Y) / 6;
      a1 = (points[i + 1].X - points[i - 1].X) / 2;
      b1 = (points[i + 1].Y - points[i - 1].Y) / 2;
      a2 = (points[i - 1].X - 2 * points[i].X + points[i + 1].X) / 2;
      b2 = (points[i - 1].Y - 2 * points[i].Y + points[i + 1].Y) / 2;
      a3 = (-points[i - 1].X + 3 * points[i].X - 3 * points[i + 1].X + points[i + 2].X) / 6;
      b3 = (-points[i - 1].Y + 3 * points[i].Y - 3 * points[i + 1].Y + points[i + 2].Y) / 6;
      start = new PointF
      (
        points[0].X + deltaX * i,
        points[0].Y + deltaY * i
      );
      end = new PointF
      (
        points[0].X + deltaX * (i + 1),
        points[0].Y + deltaY * (i + 1)
      );
      graphics.DrawCubicCurve(pen, beta, step, start, end, a3, a2, a1, a0, b3, b2, b1, b0);
    }
    {
      a0 = points[points.Length - 1].X;
      b0 = points[points.Length - 1].Y;
      a1 = points[points.Length - 2].X - points[points.Length - 1].X;
      b1 = points[points.Length - 2].Y - points[points.Length - 1].Y;
      a2 = 0;
      b2 = 0;
      a3 = (points[points.Length - 1].X - 2 * points[points.Length - 2].X + points[points.Length - 3].X) / 6;
      b3 = (points[points.Length - 1].Y - 2 * points[points.Length - 2].Y + points[points.Length - 3].Y) / 6;
      start = points[points.Length - 1];
      end = new PointF
      (
        points[0].X + deltaX * (points.Length - 2),
        points[0].Y + deltaY * (points.Length - 2)
      );
      graphics.DrawCubicCurve(pen, beta, step, start, end, a3, a2, a1, a0, b3, b2, b1, b0);
    }
  }
}

Суть в том , что в WPF не используется Graphics.DrawLine, либо я не знаю как. Но можно использовать DrawingContext.DrawLine, но не могу понять как. Может кто сталкивался и может подсказать? Код взят с https://habrahabr.ru/post/116758/