compface(3)

NAME

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

SYNOPSIS

       compface (buf)

       uncompface (buf)

       char *buf

DESCRIPTION

       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 fol-
       lowed 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.

       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.

DIAGNOSTICS

       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 over-
       run occurs.

SEE ALSO

       Compface(1)

                                25 January 1990                    COMPFACE(3)