title: ocr and image preprocessing techniques
body: <p>Hi all I have a collection of images that are similar to photos of car registration plates.</p>
  
  <p>I am wondering how to pre process the image before sending it to an OCR engine to determine the text.</p>
  
  <p>I would like to eventually be able to crop the input on only the white content of the registration plate.</p>
  
  <p>The actual image would look something like this:</p>
  
  <p><img src="https://i.stack.imgur.com/EbvAx.jpg" alt="input"></p>
  
  <p>and should end up something like this (color depth not important)
  <img src="https://i.stack.imgur.com/d8vV2.jpg" alt="ouput"></p>
  
  <p>Thank for any help.
  Regards,
  Bob</p>