title: Image processing with openCV, color change
body: <p>I am doing some image processing and I have a black shape on a white image. To use <code>findContours()</code> properly I need a white shape on a black image.</p>
  
  <ol>
  <li>Is there a way to change openCV settings to track for black shapes on white background instead ?</li>
  <li>I managed to find white part of the image using <code>inrange()</code> I change it to some other color, then change the black part to white, and then again the first part to black all using <code>inrange()</code>. But is there a easier way to convert all the black to white and white to black on the image at the same time ?</li>
  </ol>