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       compface, uncompface - compress and expand 48x48x1 face image files


       compface (buf)

       uncompface (buf)

       char *buf


       compface is a function for generating highly compressed representations
       of 48x48x1 face image files.  uncompface is an inverse  function  which
       performs an inverse transformation with no loss of data.  The algorithm
       used is highly tuned for its purpose and achieves better than a five to
       one  compression  ratio  on average.  In both functions, input is via a
       NULL terminated string and a NULL terminated output string  is  written
       over  the  input  string.   Buf should therefore point to a block of 2K
       size or more to avoid buffer overruns during output generation.

       The input format for compface (and the output format for uncompface) is
       48  lines  each of 3 sixteen bit hexadecimal integers, comma terminated
       in C initialiser style.  The output format of compface (and  the  input
       format  for  uncompface)  is  some  number  of lines made up of a space
       followed  by  printable  characters  (in  the  range  ‘‘!’’  to   ‘‘~’’
       inclusive).   The first line contains 72 characters and following lines
       contain 79 characters except that the last line may be short.

       This version of compface has been patched to also  be  able  to  handle
       normal  XBM  images.  uncompface will produce XBM output only if the -X
       switch is applied.

       The amount of compression obtained varies between face image files  but
       the  output of compface averages less than 200 characters.  The average
       number of output lines is three.


       The return value is normally 0.  1 will be returned if extra input  has
       been  ignored  during a compress operation.  -1 is returned in the case
       of an invalid input format.  -2  is  returned  if  an  internal  buffer
       overrun occurs.



                                25 January 1990