title: Pytesseract image_to_string empty output
body: <p>I have this image that was cropped from another image and I want to give this image as an input to image_to_string method:</p>
  
  <pre><code>import pytesseract
  import cv2
  num_plate = cv2.imread('E:\Images\car_plate222.jpeg' , cv2.IMREAD_GRAYSCALE)
  pytesseract.pytesseract.tesseract_cmd = r'C:\Program Files\Tesseract-OCR\tesseract.exe'
  cv2.dilate(num_plate, (15, 15), num_plate)
  pytesseract.image_to_string(num_plate)
  </code></pre>
  
  <p>Here's the photo:
  Car Plate:<br>
  <a href="https://i.stack.imgur.com/hdoKl.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/hdoKl.jpg" alt="Car Plate"></a></p>
  
  <p>I used dilation for better performance, but it doesn't give me desired output (Sometimes gives me empty string and sometimes gives me weird output)</p>
  
  <p>Does anybody know what's wrong?</p>