title: Tesseract use subset of letters
body: <p>Im using tesseract-ocr package on Ubuntu Linux, I have been using it for a while and I think that in order to improve the accuracy of the OCR I only need a subset of letters from the alphabet. The letters I need are:</p>
  
  <pre><code>0123456789abcdefghijklmnopqrstuvwxyz
  </code></pre>
  
  <p>and only that, not even capital letters, can anybody give me a hand on indicating tesseract to only match againts a subset of letters ?</p>
  
  <p>Thanks,</p>