title: How to reduce the number of colors in an image with OpenCV?
body: <p>I have a set of image files, and I want to reduce the number of colors of them to 64. How can I do this with OpenCV?</p>
  
  <p>I need this so I can work with a 64-sized image histogram. 
  I'm implementing CBIR techniques</p>
  
  <p>What I want is color quantization to a 4-bit palette.</p>