WriteableBitmap in WPF

Question

I am trying to port an application from Silverlight to WPF and would like to get some help.  I am quite experienced in the former, but not so in the latter.  It turns out to be surprisingly difficult.

I managed to get the WPF code to dual compile in Silverlight and WPF (with tons of features turned off in the WPF version, for now), but I am very much stuck with getting the equivalent of WriteableBitmap to work.

Yes WPF supports WriteableBitmap but apparently in a very different fashion.  I did some research (including going to the WPF forum) and the answers are either old or less than satisfactory.  For example, someone wants to update some line drawings 10 times a second, and the answer was "the initial implementation of WriteableBitmap did not provide adequate performance for scenarios like yours".  Really?

So does anyone have a solution to this problem?  Ideally it would satisfy the following:

(1) Use WriteableBitmap or something equivalent that allows easy read/write access to the pixels, without having to copy in/out the whole thing for each access.

(2) Allow the use of WriteableBitmap.Render() and Invalidate() or something equivalent.

As an example, I would like to get the following code working in <1 seconds (certainly doable in Silverlight).  The code is meaningless other than to demonstrate what I would like to be able to achieve in reasonable amount of time.

Image image = makeImage();  // some 100x100 image;
WriteableBitmap wb = new WriteableBitmap(1024, 768);
for (int i = 0; i < 256; i++) wb.Render(image, getTransform(i));  // draw the same image 256 times, with offsets;
wb.Invalidate();
int count = 0;
for (int i = 0; i < 1024 * 768; i++)
  if (((wb.Pixels[ i ] >> 24) & 0xff) > 0) count++;

Your help would be appreciated.  Thanks!

Answer 1

ok read this carefully :

The Idea is using Parallel Extensions and enhancing the multi threading issues

http://khason.net/blog/how-to-high-performance-graphics-in-wpf/

Answer 2

Thank you for your answer and I indeed read the article carefully.  It does not solve my problem though.  I understand the principle behind the technique, but I want something somewhat compatible with the Silverlight version of WriteableBitmap.  Faster bitmap manipulation is something that I've figured out already, but I haven't figured out how to do that and Render() and Invalidate() at the same time.

Answer 3

contact David:

http://channel9.msdn.com/Blogs/AdamKinney/WPF-35-SP1-Graphics-with-David-Teitlebaum