title: regionprops returning single result
body: <p>I do not understand the function 'regionprops' properly. For example if I create a binary matrix with three different areas, it only gives me a single centerpoint as output:</p>
  
  <pre><code>a  = zeros(100,100);
  a(1:49,1:49)    = 1;
  a(1:25,75:100)  = 1;
  a(51:100,51:100)= 1;
  spy(a)
  
  regionprops(a,'Centroid')
  </code></pre>
  
  <p>But if I add the line </p>
  
  <pre><code>    a=bwmorph(a,'erode',0);
  </code></pre>
  
  <p>which does absolutely nothing, I get three different center points as output, one for each area. Why do they give different outputs and is it really necesarry to add a useless line of code?</p>