title: Using Python Pillow lib to set Color depth
body: <p>I am using the Python Pillow lib to change an image before sending it to device.
  I need to change the image to make sure it meets the following requirements</p>
  
  <ul>
  <li>Resolution (width x height) = 298 x 144 </li>
  <li>Grayscale </li>
  <li>Color Depth (bits) = 4 </li>
  <li>Format = .png</li>
  </ul>
  
  <p>I can do all of them with the exception of Color Depth to 4 bits.
  Can anyone point me in the right direction on how to achieve this?</p>