title: How do I calculate the percentage of difference between two images using Python and OpenCV?
body: <p>I am trying to write a program in Python (with OpenCV) that compares 2 images, shows the difference between them, and then informs the user of the percentage of difference between the images.  I have already made it so it generates a .jpg showing the difference, but I can't figure out how to make it calculate a percentage.  Does anyone know how to do this?</p>
  
  <p>Thanks in advance.</p>