Multiple Image Processing

   Since a  GIF  data  stream  can  contain  multiple  images,  it  is
   necessary  to  describe  processing and display of such a file.  Because
   the image descriptor allows  for  placement  of  the  image  within  the
   logical  screen,  it is possible to define a sequence of images that may
   each be a partial screen, but in total  fill  the  entire  screen.   The
   guidelines for handling the multiple image situation are:

   1.  There is no pause between images.  Each is processed immediately  as
       seen by the decoder.

   2.  Each image explicitly overwrites any image  already  on  the  screen
       inside  of  its window.  The only screen clears are at the beginning
       and end of the  GIF  image  process.   See  discussion  on  the  GIF
       terminator.