Question

I am currently working on a C# application that uses Drawing.Graphics to draw to a Bitmap which I display in a picture box. I am rendering a graph with a grid, so I have to draw about 200 grid lines in addition to a number of points onscreen. I can scroll to move around the graph, but while doing so, I notice that my drawing function has poor performance as it stutters. Replacing this approach with OpenTK and its GLControl class makes rendering so efficient that scrolling is very smooth.

Is there any way to get faster performance from Drawing.Graphics?

  // This is only done when the window is resized
  Bitmap bmp = new Bitmap(picRender.Width, picRender.Height);
  Graphics g = Graphics.FromImage(bmp);

  // Drawing code
  g.Clear(picRender.BackColor);
  g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighSpeed;
  g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.Bilinear;
  if (background != null)
  {
   g.DrawImage(background, new Rectangle(0, 0, picRender.Width, picRender.Height));
  }

  for (int n = 0; n < trajectories.Count; n++)
  {
   Trajectory trajectory = trajectories[n];

   Pen pen = new Pen(new SolidBrush(TrajectoryColors[n % TrajectoryColors.Length]));

   if (RenderLines)
   {
    for (int i = 0; i < trajectory.samples.Count - 1; i++)
    {
        if (Interval_Start > trajectory.samples[i + 1].time ||
         Interval_End < trajectory.samples[i].time) { continue; }

        g.DrawLine(pen, coordinate_system.ToPoint(trajectory.samples[i].coordinates),
         coordinate_system.ToPoint(trajectory.samples[i + 1].coordinates));
    }
   }
  }
  // End of drawing

Answer 1

Next to optimizing the drawing code another tactic that can be used is buffering the results.

By not redrawing the entire image each and every time but only update parts that just scrolled into view (or better: are about to scroll into view)

If you need more information we need to see some code to help you profile.