g4tdecod.c

串口通信,传真G3_G4编解码源代码,对如何编解码有用处.

	  }
	  else /* color == BLACK */
	  {
	    (*p_decode_black) ((short) (b1 - a0));
	    color = WHITE;
	  }
	  a0 = b1; 
          if (current_row == EVEN)
          {
	    even_runs [++even_index] = a0;
	    odd_index++;
          }
          else /* current_row == ODD */
          {
	    odd_runs [++odd_index] = a0;
	    even_index++;
          }
          bit_number = next_state;
          break;
        case VERTICAL_VR1_MODE: /* the next color change begins one pixel to the
          right of its location on the previous row */
	  #if defined (TRACE)
            if (row_number >= TRACE_BEGIN && row_number <= TRACE_END)
              printf (" VR1 ");
	  #endif
	  if (color == WHITE)
	  {
	    (*p_decode_white) ((short) (b1 - a0 + 1));
	    color = BLACK;
	  }
	  else /* color == BLACK */
	  {
	    (*p_decode_black) ((short) (b1 - a0 + 1));
	    color = WHITE;
	  }
	  a0 = b1 + 1; 
          if (current_row == EVEN)
          {
	    even_runs [++even_index] = a0;
	    odd_index++;
          }
          else /* current_row == ODD */
          {
	    odd_runs [++odd_index] = a0;
	    even_index++;
          }
          bit_number = next_state;
          break;
        case VERTICAL_VR2_MODE: /* the next color change begins two pixels to
          the right of its location on the previous row */
	  #if defined (TRACE)
            if (row_number >= TRACE_BEGIN && row_number <= TRACE_END)
              printf (" VR2 ");
	  #endif
	  if (color == WHITE)
	  {
	    (*p_decode_white) ((short) (b1 - a0 + 2));
	    color = BLACK;
	  }
	  else /* color == BLACK */
	  {
	    (*p_decode_black) ((short) (b1 - a0 + 2));
	    color = WHITE;
	  }
	  a0 = b1 + 2; 
          if (current_row == EVEN)
          {
	    even_runs [++even_index] = a0;
	    odd_index++;
          }
          else /* current_row == ODD */
          {
	    odd_runs [++odd_index] = a0;
	    even_index++;
          }
          bit_number = next_state;
          break;
        case VERTICAL_VR3_MODE: /* the next color change begins three pixels to
          the right of its location on the previous row */
	  #if defined (TRACE)
            if (row_number >= TRACE_BEGIN && row_number <= TRACE_END)
              printf (" VR3 ");
	  #endif
	  if (color == WHITE)
	  {
	    (*p_decode_white) ((short) (b1 - a0 + 3));
	    color = BLACK;
	  }
	  else /* color == BLACK */
	  {
	    (*p_decode_black) ((short) (b1 - a0 + 3));
	    color = WHITE;
	  }
	  a0 = b1 + 3; 
          if (current_row == EVEN)
          {
	    even_runs [++even_index] = a0;
	    odd_index++;
          }
          else /* current_row == ODD */
          {
	    odd_runs [++odd_index] = a0;
	    even_index++;
          }
          bit_number = next_state;
          break;
        case VERTICAL_VL1_MODE: /* the next color change begins one pixel to the
          left of its location on the previous row */
	  #if defined (TRACE)
            if (row_number >= TRACE_BEGIN && row_number <= TRACE_END)
              printf (" VL1 ");
	  #endif
	  if (color == WHITE)
	  {
	    (*p_decode_white) ((short) (b1 - a0 - 1));
	    color = BLACK;
	  }
	  else /* color == BLACK */
	  {
	    (*p_decode_black) ((short) (b1 - a0 - 1));
	    color = WHITE;
	  }
	  a0 = b1 - 1; 
          if (current_row == EVEN)
          {
	    even_runs [++even_index] = a0;
	    odd_index++;
          }
          else /* current_row == ODD */
          {
	    odd_runs [++odd_index] = a0;
	    even_index++;
          }
          bit_number = next_state;
          break;
        case VERTICAL_VL2_MODE: /* the next color change begins two pixels to
          the left of its location on the previous row */
	  #if defined (TRACE)
            if (row_number >= TRACE_BEGIN && row_number <= TRACE_END)
              printf (" VL2 ");
	  #endif
	  if (color == WHITE)
	  {
	    (*p_decode_white) ((short) (b1 - a0 - 2));
	    color = BLACK;
	  }
	  else /* color == BLACK */
	  {
	    (*p_decode_black) ((short) (b1 - a0 - 2));
	    color = WHITE;
	  }
	  a0 = b1 - 2; 
          if (current_row == EVEN)
          {
	    even_runs [++even_index] = a0;
	    if (a0 < b0) odd_index--;
	    else odd_index++;
          }
          else /* current_row == ODD */
          {
	    odd_runs [++odd_index] = a0;
	    if (a0 < b0) even_index--;
	    else even_index++;
          }
          bit_number = next_state;
          break;
        case VERTICAL_VL3_MODE: /* the next color change begins three pixels to
          the left of its location on the previous row */
	  #if defined (TRACE)
            if (row_number >= TRACE_BEGIN && row_number <= TRACE_END)
              printf (" VL3 ");
	  #endif
	  if (color == WHITE)
	  {
	    (*p_decode_white) ((short) (b1 - a0 - 3));
	    color = BLACK;
	  }
	  else /* color == BLACK */
	  {
	    (*p_decode_black) ((short) (b1 - a0 - 3));
	    color = WHITE;
	  }
	  a0 = b1 - 3; 
          if (current_row == EVEN)
          {
	    even_runs [++even_index] = a0;
	    if (a0 < b0) odd_index--;
	    else odd_index++;
          }
          else /* current_row == ODD */
          {
	    odd_runs [++odd_index] = a0;
	    if (a0 < b0) even_index--;
	    else even_index++;
          }
          bit_number = next_state;
          break;
        case EXT_MODE_UNCOMPRESSED: /* enter extension type 7 ("111"), an
          uncompressed encoding scheme */
          return (ERROR_UNSUPPORTED_EXTENSION);
          break;
        case ERROR_MODE: /* The bit pattern found corresponds to an unknown or
          invalid codeword.  This MAY be one of the seven possible extensions
          not defined by the specification. */
          return (ERROR_INVALID_CODEWORD);
          break;
        case ERROR_MODE_1: /* assumed in this implementation to be equivalent
          to EOFB (end-of-facsimile-block) */
          return (RETURN_OK);
          break;
        default: /* we should never get here; if we do, the tables are bad */
          return (ERROR_PROGRAM_LOGIC);
          break;
      }
    }
    if (a0 >= column_limit) new_row ();
  }
  return (decode_return);
}

/* g4i_initialize () is called to set up to decode a new image.  All of the
   static data (flags, etc) for g4i_decode () are initialized, allowing the
   decoding of multiple images in a run as long as g4i_initialize () is
   called before each one. */
char g4i_initialize (short image_width, short image_length)
{
  color = WHITE;
  bit_number= 0;
  current_row = ODD;
  even_runs [0] = 0;
  even_runs [1] = image_width; /* initial b1 */
  even_runs [2] = image_width; /* initial b2 */
  odd_runs [0] = 0;
  a0 = 0;
  even_index = 1; odd_index = 0;
  column_limit = image_width;
  row_number = 0;
  b1 = -1;
  decode_return = 0;
  return (0);
}

static void new_row ()
{
  (*p_decode_new_row) ();
  color = WHITE;
  if (current_row == ODD)
  {
    current_row = EVEN;
    odd_runs [++odd_index] = a0;
    odd_runs [++odd_index] = a0;
    odd_index = 1;
    even_index = 0;
  }
  else /* current_row == EVEN */
  {
    current_row = ODD;
    even_runs [++even_index] = a0;
    even_runs [++even_index] = a0;
    even_index = 1;
    odd_index = 0;
  }
  a0 = 0;
  b1 = -1;
  #if defined (TRACE)
    row_number++;
  #endif
}

static short run_length_table [] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
  13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31,
  32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50,
  51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 128, 192, 256, 320,
  384, 448, 512, 576, 640, 704, 768, 832, 896, 960, 1024, 1088, 1152, 1216,
  1280, 1344, 1408, 1472, 1536, 1600, 1664, 1728, 1792, 1856, 1920, 1984,
  2048, 2112, 2176, 2240, 2304, 2368, 2432, 2496, 2560};

static short decode_black_run ()
{
  short runlength, accum_runlength = 0;
  next_state = (unsigned char) (bit_number + 8);
  for (;;) /* exit with "return" */
  {
    if (!bit_number) code_byte = (*p_decode_next_byte) ();
	 /* this will fetch a new byte
	    if the previous codeword ended on a byte boundary */
    mode = horiz_mode [next_state] [code_byte];
    next_state = horiz_mode_next_state [next_state] [code_byte];
    if (mode) /* if digestible */
    {
      bit_number = next_state;
      runlength = run_length_table [mode - 106];
      accum_runlength += runlength;
      if (runlength < 64) return (accum_runlength);
      next_state += 8;
    }
    else bit_number = 0;
  }
}

static short decode_white_run ()
{
  short runlength, accum_runlength = 0;
  next_state = (unsigned char) bit_number;
  for (;;) /* exit with "return" */
  {
    if (!bit_number) code_byte = (*p_decode_next_byte) ();
	 /* this will fetch a new byte
	    if the previous codeword ended on a byte boundary */
    mode = horiz_mode [next_state] [code_byte];
    next_state = horiz_mode_next_state [next_state] [code_byte];
    if (mode) /* if digestible */
    {
      bit_number = next_state;
      runlength = run_length_table [mode - 2];
      accum_runlength += runlength;
      if (runlength < 64) return (accum_runlength);
    }
    else bit_number = 0;
  }
}

/*	end $RCSfile: g4tdecod.c $ */