title: Allow an Image to be accessed by several threads
body: <p>I'm trying to do some image processing in C#.
  I want to use some threads to do parallel computations on several zones in my image.
  Threads are actually getting and setting pixels in a Bitmap object. There is absolutely no chance for 2 threads to access the same pixel, so that's not the problem.</p>
  
  <p>The problem is that C# doesnt allow me to start several threads on the same Bitmap object, even if i'm sure that the same pixel won't be read and modified simultaneously.</p>
  
  <p>Is there any way to avoid C# to raise this error ? Or is it just impossible to run several threads on my Bitmap object ?</p>
  
  <p>Thank you,</p>
  
  <p>Pierre-Olivier</p>