title: Image Poisson Noise on image in double precision (shot noise)
body: <p>I am trying to add poisson noise to an image with doulbe precision. I do:</p>
  
  <pre><code>I = im2double(imread('mypic.tif')); % mypic.tif is already in the range 0...1 in double precision
  J = imnoise(I,'poisson');
  imshow(I),figure,imshow(J);
  </code></pre>
  
  <p>I see that both <code>I</code> and <code>J</code> are pretty the same. What I am doing wrong?<br>
  Please note I do know that imnoise scales the value by 1e-12 but sincerly I don't understand how to use it correctly.</p>
  
  <p>I was thinking I could use <code>poissrnd()</code> to add noise manually to bypass <code>imnoise</code> </p>
  
  <p>Regarding the scaling i was using a <a href="http://www.mathworks.com/matlabcentral/newsreader/view_thread/242444#621859" rel="nofollow">code like this</a>:</p>
  
  <pre><code>maxValue = max(I(:));
  
  % This is necessary based on imnoise behaviour
  I = I * 10e-12;
  
  % Generate noisy image and scale back to the original intensities. 
  J = maxValue * imnoise(I, 'poisson'); 
  </code></pre>
  
  <p>But it returns an image almost completly black. </p>