title: Python PIL to extract number from image
body: <p>I have an image like this one:
  <img src="https://i.stack.imgur.com/wjNL6.jpg" alt="number"></p>
  
  <p>and I would like to have a black number written on white so that I can use an OCR to recognise it. How could I achieve that in Python?</p>
  
  <p>Many thanks,</p>
  
  <p>John.</p>