Performance of WriteableBitmapEx

Question

I am generating a full screen image with 37000 or so markers. To do this I use the following code

    private void DrawMarkers(WriteableBitmap bitmap)
    {

            WriteableBitmap marker = BitmapFactory.New(5, 5);
            var sourceRect = new Rect(0, 0, 5, 5);
            marker.DrawEllipseCentered(3, 3, 2, 2, Colors.Blue);
            var s = Stopwatch.StartNew();
            foreach (var point in TransformedPoints)
            {
                bitmap.Blit(new Rect((int)point.X, (int)point.Y, 5, 5), marker, sourceRect);
            }
            s.Stop();
            Console.WriteLine("Blitting " + 
                 TransformedPoints.Count + 
                 " Points took " + 
                 s.ElapsedMilliseconds + " ms");

    }

To blit these 37000 points it takes approximately 203 ms on my EliteBook 8770w Windows7. I've gone down from using standard WPF framework elements to drawingVisuals and now to writeable bitmap. I need real time zoom on this set of markers so the markers need redrawing. I would say I need about 50ms for a redraw for it to be ok.

From what I read WriteableBitmap is the lowest level I can go. What is the next step in performance improvement can I go. It seems this needs to be delegated to the GPU. How could I do this in C# or what libraries should I use?

score 3 · Answer 1 · answered Mar 22 '13 at 13:21

One big improvement would be to use leverage the BitmapContext concept so you don't lock and unlock all the time and avoid too many pixel copies.

using (marker.GetBitmapContext(ReadWriteMode.ReadOnly))
{
    using(bitmap.GetContext())
    {    
        foreach (var point in TransformedPoints)
        {
            bitmap.Blit(new Rect((int)point.X, (int)point.Y, 5, 5), marker, sourceRect);
        }
    }
}

And you should provide the BlendMode.None if you don't need alpha blending:

bitmap.Blit(new Rect((int)point.X, (int)point.Y, 5, 5), marker, sourceRect, BlendMode.None);

rene

Performance of WriteableBitmapEx

1 Answers1