title: HAAR Cascade type of images for recognising cars
body: <p>I want to write a python script to highlight cars in a picture (with a reactangle (OPENCV)).
  I'm going to make a HAAR Cascade, but I'm a bit stuck. I read a lot about it, and I have some concerns.</p>
  <p>I'm planning on using pictures of cars without a background (no road or anything like that) as my <strong>positive images</strong>.
  As <strong>negative images</strong> I would use empty roads.</p>
  <p>Also I'd like to know how many pictures should I get? On forums I've read that I would need 1000 <strong>positive</strong> and 10 000 <strong>negative</strong> pictures.</p>
  <p>Is my thought process correct?</p>