/*# proc: bits2bytes - promotes a binary image to a grayscale image.# proc:        destination pointer must be double-aligned.# proc:        not generalized by byte-order.# proc:*/#include <stdio.h>#include <values.h>#include <sys/param.h>#include <sys/types.h>bits2bytes(p,q,pixels)u_char *p, *q;u_int pixels;{double **rptrs, *dst;static u_char *ptrs[1 << BITSPERBYTE];static int init = 0;   if (p == (u_char *) NULL)      fatalerr("bits2bytes", "source data pointer is", "NULL");   if (q == (u_char *) NULL)      fatalerr("bits2bytes", "destination data pointer is", "NULL");   if (!init)   {      int i, j;      u_char *r;      static u_char table[(1 << BITSPERBYTE) * BITSPERBYTE];      static u_char mask[BITSPERBYTE] =         { 0x80, 0x40, 0x20, 0x10, 0x08, 0x04, 0x02, 0x01 };      for ( r = table, i = 0 ; i < (1 << BITSPERBYTE) ; i++ )         for ( j = 0, ptrs[i] = r ; j < BITSPERBYTE; j++ )            *r++ = (i & mask[j]) ? 1 : 0;      init = 1;   }   pixels = howmany(pixels,BITSPERBYTE);   for ( dst = (double *)q, rptrs = (double **)ptrs ; pixels-- ; )      *dst++ = *rptrs[*p++];}