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?

Rene Schulte · Accepted Answer · 2013-03-22 13:21:50Z

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

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