xgprintgif.c

xgrafix 是PTSG模拟程序中的图形截面库 改版本是最新版本

		      int Background, int BitsPerPixel, int Red[], int Green[],
		      int Blue[], ifunptr GetPixel) {
  int B;
  int RWidth, RHeight;
  int LeftOfs, TopOfs;
  int Resolution;
  int ColorMapSize;
  int InitCodeSize;
  int i;
  
  Interlace = GInterlace;
  
  ColorMapSize = 1 << BitsPerPixel;
  
  RWidth = Width = GWidth;
  RHeight = Height = GHeight;
  LeftOfs = TopOfs = 0;
  
  Resolution = BitsPerPixel;
  
  /*
   * Calculate number of bits we are expecting
   */
  CountDown = (long)Width * (long)Height;
  
  /*
   * Indicate which pass we are on (if interlace)
   */
  Pass = 0;
  
  /*
   * The initial code size
   */
  if( BitsPerPixel <= 1 )
    InitCodeSize = 2;
  else
    InitCodeSize = BitsPerPixel;
  
  /*
   * Set up the current x and y position
   */
  curx = cury = 0;
  
  /*
   * Write the Magic header
   */
  fwrite( "GIF87a", 1, 6, fp );
  
  /*
   * Write out the screen width and height
   */
  Putword( RWidth, fp );
  Putword( RHeight, fp );
  
  /*
   * Indicate that there is a global colour map
   */
  B = 0x80;       /* Yes, there is a color map */
  
  /*
   * OR in the resolution
   */
  B |= (Resolution - 1) << 5;
  
  /*
   * OR in the Bits per Pixel
   */
  B |= (BitsPerPixel - 1);
  
  /*
   * Write it out
   */
  fputc( B, fp );
  
  /*
   * Write out the Background colour
   */
  fputc( Background, fp );
  
  /*
   * Byte of 0's (future expansion)
   */
  fputc( 0, fp );
  
  /*
   * Write out the Global Colour Map
   */
  for( i=0; i<ColorMapSize; ++i ) {
    fputc( Red[i], fp );
    fputc( Green[i], fp );
    fputc( Blue[i], fp );
  }
  
  /*
   * Write an Image separator
   */
  fputc( ',', fp );
  
  /*
   * Write the Image header
   */
  
  Putword( LeftOfs, fp );
  Putword( TopOfs, fp );
  Putword( Width, fp );
  Putword( Height, fp );
  
  /*
   * Write out whether or not the image is interlaced
   */
  if( Interlace )
    fputc( 0x40, fp );
  else
    fputc( 0x00, fp );
  
  /*
   * Write out the initial code size
   */
  fputc( InitCodeSize, fp );
  
  /*
   * Go and actually compress the data
   */
  compress( InitCodeSize+1, fp, GetPixel );
  
  /*
   * Write out a Zero-length packet (to end the series)
   */
  fputc( 0, fp );
  
  /*
   * Write the GIF file terminator
   */
  fputc( ';', fp );
  
  /*
   * And let the calling routine close the file
   */
  /* fclose( fp ); */
}

/*
 * Write out a word to the GIF file
 */
static void Putword( int w, FILE* fp) {
  fputc( w & 0xff, fp );
  fputc( (w / 256) & 0xff, fp );
}


/***************************************************************************
 *
 *  GIFCOMPR.C       - GIF Image compression routines
 *
 *  Lempel-Ziv compression based on 'compress'.  GIF modifications by
 *  David Rowley ([e-mail])
 *
 ***************************************************************************/

/*
 * General DEFINEs
 */

/*
 *
 * GIF Image compression - modified 'compress'
 *
 * Based on: compress.c - File compression ala IEEE Computer, June 1984.
 *
 * By Authors:  Spencer W. Thomas       (decvax!harpo!utah-cs!utah-gr!thomas)
 *              Jim McKie               (decvax!mcvax!jim)
 *              Steve Davies            (decvax!vax135!petsd!peora!srd)
 *              Ken Turkowski           (decvax!decwrl!turtlevax!ken)
 *              James A. Woods          (decvax!ihnp4!ames!jaw)
 *              Joe Orost               (decvax!vax135!petsd!joe)
 *
 */


/*
 * To save much memory, we overlay the table used by compress() with those
 * used by decompress().  The tab_prefix table is the same size and type
 * as the codetab.  The tab_suffix table needs 2**BITS characters.  We
 * get this from the beginning of htab.  The output stack uses the rest
 * of htab, and contains characters.  There is plenty of room for any
 * possible stack (stack used to be 8000 characters).
 */


/*
 * compress stdin to stdout
 *
 * Algorithm:  use open addressing double hashing (no chaining) on the
 * prefix code / next character combination.  We do a variant of Knuth's
 * algorithm D (vol. 3, sec. 6.4) along with G. Knott's relatively-prime
 * secondary probe.  Here, the modular division first probe is gives way
 * to a faster exclusive-or manipulation.  Also do block compression with
 * an adaptive reset, whereby the code table is cleared when the compression
 * ratio decreases, but after the table fills.  The variable-length output
 * codes are re-sized at this point, and a special CLEAR code is generated
 * for the decompressor.  Late addition:  construct the table according to
 * file size for noticeable speed improvement on small files.  Please direct
 * questions about this implementation to ames!jaw.
 */

static void compress( int init_bits, FILE* outfile, ifunptr ReadValue) {
  register long fcode;
  register code_int i /* = 0 */;
  register int c;
  register code_int ent;
  register code_int disp;
  register code_int hsize_reg;
  register int hshift;
  
  /*
   * Set up the globals:  g_init_bits - initial number of bits
   *                      g_outfile   - pointer to output file
   */
  g_init_bits = init_bits;
  g_outfile = outfile;
  
  /*
   * Set up the necessary values
   */
  offset = 0;
  out_count = 0;
  clear_flg = 0;
  in_count = 1;
  maxcode = MAXCODE(n_bits = g_init_bits);
  
  ClearCode = (1 << (init_bits - 1));
  EOFCode = ClearCode + 1;
  free_ent = ClearCode + 2;
  
  char_init();
  
  ent = GIFNextPixel( ReadValue );
  
  hshift = 0;
  for ( fcode = (long) hsize;  fcode < 65536L; fcode *= 2L )
    ++hshift;
  hshift = 8 - hshift;                /* set hash code range bound */
  
  hsize_reg = hsize;
  cl_hash( (count_int) hsize_reg);            /* clear hash table */
  
  output( (code_int)ClearCode );
  
#ifdef SIGNED_COMPARE_SLOW
  while ( (c = GIFNextPixel( ReadValue )) != (unsigned) EOF ) {
#else /*SIGNED_COMPARE_SLOW*/
  while ( (c = GIFNextPixel( ReadValue )) != EOF ) {	/* } */
#endif /*SIGNED_COMPARE_SLOW*/

    ++in_count;
    
    fcode = (long) (((long) c << maxbits) + ent);
    i = (((code_int)c << hshift) ^ ent);    /* xor hashing */
    
    if ( HashTabOf (i) == fcode ) {
      ent = CodeTabOf (i);
      continue;
    } else if ( (long)HashTabOf (i) < 0 )      /* empty slot */
      goto nomatch;
    disp = hsize_reg - i;           /* secondary hash (after G. Knott) */
    if ( i == 0 )
      disp = 1;
  probe:
    if ( (i -= disp) < 0 )
      i += hsize_reg;
    
    if ( HashTabOf (i) == fcode ) {
      ent = CodeTabOf (i);
      continue;
    }
    if ( (long)HashTabOf (i) > 0 )
      goto probe;
  nomatch:
    output ( (code_int) ent );
    ++out_count;
    ent = c;
#ifdef SIGNED_COMPARE_SLOW
    if ( (unsigned) free_ent < (unsigned) maxmaxcode) {
#else /*SIGNED_COMPARE_SLOW*/
    if ( free_ent < maxmaxcode ) {	/* } */
#endif /*SIGNED_COMPARE_SLOW*/
      CodeTabOf (i) = free_ent++; /* code -> hashtable */
      HashTabOf (i) = fcode;
    } else
      cl_block();
  }
  /*
   * Put out the final code.
   */
  output( (code_int)ent );
  ++out_count;
  output( (code_int) EOFCode );
}

/*****************************************************************
 * TAG( output )
 *
 * Output the given code.
 * Inputs:
 *      code:   A n_bits-bit integer.  If == -1, then EOF.  This assumes
 *              that n_bits =< (long)wordsize - 1.
 * Outputs:
 *      Outputs code to the file.
 * Assumptions:
 *      Chars are 8 bits long.
 * Algorithm:
 *      Maintain a BITS character long buffer (so that 8 codes will
 * fit in it exactly).  Use the VAX insv instruction to insert each
 * code in turn.  When the buffer fills up empty it and start over.
 */

static void output(code_int  code) {
  cur_accum &= masks[ cur_bits ];
  
  if( cur_bits > 0 )
    cur_accum |= ((long)code << cur_bits);
  else
    cur_accum = code;
  
  cur_bits += n_bits;

  while( cur_bits >= 8 ) {
    char_out( (unsigned int)(cur_accum & 0xff) );
    cur_accum >>= 8;
    cur_bits -= 8;
  }
  
  /*
   * If the next entry is going to be too big for the code size,
   * then increase it, if possible.
   */
  if ( free_ent > maxcode || clear_flg ) {
    
    if( clear_flg ) {
      
      maxcode = MAXCODE (n_bits = g_init_bits);
      clear_flg = 0;
      
    } else {
      
      ++n_bits;
      if ( n_bits == maxbits )
	maxcode = maxmaxcode;
      else
	maxcode = MAXCODE(n_bits);
    }
  }
  
  if( code == EOFCode ) {
    /*
     * At EOF, write the rest of the buffer.
     */
    while( cur_bits > 0 ) {
      char_out( (unsigned int)(cur_accum & 0xff) );
      cur_accum >>= 8;
      cur_bits -= 8;
    }
    
    flush_char();
    
    fflush( g_outfile );
    
  }
}

/*
 * Clear out the hash table
 */
static void cl_block () {             /* table clear for block compress */
  cl_hash ( (count_int) hsize );
  free_ent = ClearCode + 2;
  clear_flg = 1;
  
  output( (code_int)ClearCode );
}

static void cl_hash(register count_int hsize) {         /* reset code table */
  register count_int *htab_p = htab+hsize;
  
  register long i;
  register long m1 = -1;
  
  i = hsize - 16;
  do {                            /* might use Sys V memset(3) here */
    *(htab_p-16) = m1;
    *(htab_p-15) = m1;
    *(htab_p-14) = m1;
    *(htab_p-13) = m1;
    *(htab_p-12) = m1;
    *(htab_p-11) = m1;
    *(htab_p-10) = m1;
    *(htab_p-9) = m1;
    *(htab_p-8) = m1;
    *(htab_p-7) = m1;
    *(htab_p-6) = m1;
    *(htab_p-5) = m1;
    *(htab_p-4) = m1;
    *(htab_p-3) = m1;
    *(htab_p-2) = m1;
    *(htab_p-1) = m1;
    htab_p -= 16;
  } while ((i -= 16) >= 0);
  
  for ( i += 16; i > 0; --i )
    *--htab_p = m1;
}

/******************************************************************************
 *
 * GIF Specific routines
 *
 ******************************************************************************/

/*
 * Number of characters so far in this 'packet'
 */

/*
 * Set up the 'byte output' routine
 */
static void char_init() {
  a_count = 0;
}

/*
 * Define the storage for the packet accumulator
 */

/*
 * Add a character to the end of the current packet, and if it is 254
 * characters, flush the packet to disk.
 */
static void char_out( int c ) {
  accum[ a_count++ ] = c;
  if( a_count >= 254 )
    flush_char();
}

/*
 * Flush the packet to disk, and reset the accumulator
 */
static void flush_char() {
  if( a_count > 0 ) {
    fputc( a_count, g_outfile );
    fwrite( accum, 1, a_count, g_outfile );
    a_count = 0;
  }
}

/* The End */

#endif