title: Screen overlay with Python, paint over an active window with background python script
body: <p>I'm writing a python script that runs in the background and takes screenshots of another application that is active. Then it analyses the screenshots and now it should overlay a certain image over the active app or the screen. I still need to be able to make mouse and keyboard inputs in the active app.</p>
  
  <p>So I need a way to overlay/paint on another window or on the screen, and still keep the other window the active window so that I can make inputs.</p>
  
  <p>I would prefer to do that with python in Mac OS, but if it isn't possible, other languages and even Windows (if really necessary) would also be ok.</p>
  
  <p>Can anybody help me?</p>
  
  <p>Thanks in advance!</p>