title: Tesseract OCR - specify pattern
body: <p>I'm trying to perform OCR using Tesseract (version 3.04.00).
  All my images have the same pattern (digit dot digit digit, ie. a decimal with 2 digits precision). I tried using the <code>--user-patterns</code> option, but I can't have it to work.</p>
  
  <p>What I did:</p>
  
  <ul>
  <li>create a file <code>patterns.txt</code> with <code>\d.\d\d</code> on first line</li>
  <li>use option <code>--user-patterns patterns.txt</code></li>
  </ul>
  
  <p>But I get the following error:</p>
  
  <pre><code>pytesseract.pytesseract.TesseractError: (1, "Tesseract Open Source OCR Engine v3.04.00 with Leptonica read_params_file: Can't open 1 read_params_file: Can't open user-patterns read_params_file: parameter not found: \\d.\\d\\d")
  </code></pre>
  
  <p>How can I specify my pattern to Tesseract ? Is this even the right approach ?
  Thanks in advance for help or advices, I don't find much doc on Tesseract.</p>
  
  <p><em>EDIT</em>: add Python code</p>
  
  <pre><code>img = cv2.imread("path/to/image", cv2.IMREAD_GRAYSCALE)
  text = pytesseract.image_to_string(img, config="-psm 7 --user-patterns patterns.txt")
  print(text)
  </code></pre>