title: GDI+:How to overlay an image on top of another one?(without using Graphics object)
body: <p>I'm working on a solution that enables our users to draw annotations over images.So far I'm using graphics object to draw an image(annotations) over another one.
  The problem is that we can't always get a Graphics object from an image(GDI+ throws an exception if we try to get a graphics object of an indexed formatted image)</p>
  
  <p>So the question is :</p>
  
  <p>what are my options to solve this problem?  can I change the PixelFormat temporarily ,get a graphics object ,do my painting and retrieve it back to its original format or can I draw an image over another one without using Graphics object?</p>