title: Find Black Squares in Image ( matlab )
body: <p>i have hundreds of paper-forms and i want to automatically read this forms. 
  The first step would be to calibrate the scanned paper. ( find the coordinates of the 4 squares )</p>
  
  <p>But i don't know how to do it in matlab :(</p>
  
  <p>here is the picture : 
  <img src="https://i.stack.imgur.com/kFZyu.png" alt="http://i.imgur.com/wR463.png"></p>