/*
 * xvgifwr.c  -  handles writing of GIF files.  based on flgife.c and
 *               flgifc.c from the FBM Library, by Michael Maudlin
 *
 * Contains: 
 *   WriteGIF(fp, pic, ptype, w, h, rmap, gmap, bmap, numcols, colorstyle,
 *            comment)
 *
 * Note: slightly brain-damaged, in that it'll only write non-interlaced 
 *       GIF files (in the interests of speed, or something)
 *
 */



/*****************************************************************
 * Portions of this code Copyright (C) 1989 by Michael Mauldin.
 * Permission is granted to use this file in whole or in
 * part for any purpose, educational, recreational or commercial,
 * provided that this copyright notice is retained unchanged.
 * This software is available to all free of charge by anonymous
 * FTP and in the UUNET archives.
 *
 *
 * Authors:  Michael Mauldin (mlm@cs.cmu.edu)
 *           David Rowley (mgardi@watdcsu.waterloo.edu)
 *
 * Based on: compress.c - File compression ala IEEE Computer, June 1984.
 *
 *	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)
 *****************************************************************/
 
/* Copyright Notice
 * ================
 * Copyright 1989, 1990, 1991, 1992, 1993 by John Bradley
 * 
 * Permission to use, copy, and distribute XV in its entirety, for 
 * non-commercial purposes, is hereby granted without fee, provided that
 * this license information and copyright notice appear in all copies.
 * 
 * Note that distributing XV 'bundled' in with ANY product is considered
 * to be a 'commercial purpose'.
 *
 * Also note that any copies of XV that are distributed MUST be built
 * and/or configured to be in their 'unregistered copy' mode, so that it
 * is made obvious to the user that XV is shareware, and that they should
 * consider donating, or at least reading this License Info.
 * 
 * The software may be modified for your own purposes, but modified
 * versions may NOT be distributed without prior consent of the author.
 * 
 * This software is provided 'as-is', without any express or implied
 * warranty.  In no event will the author be held liable for any damages
 * arising from the use of this software.
 * 
 * If you would like to do something with XV that this copyright
 * prohibits (such as distributing it with a commercial product, 
 * using portions of the source in some other program, etc.), please
 * contact the author (preferably via email).  Arrangements can
 * probably be worked out.
 *
 * XV is shareware for PERSONAL USE only.  You may use XV for your own
 * amusement, and if you find it nifty, useful, generally cool, or of
 * some value to you, your non-deductable donation would be greatly
 * appreciated.  $25 is the suggested donation, though, of course,
 * larger donations are quite welcome.  Folks who donate $25 or more
 * can receive a Real Nice bound copy of the XV manual for no extra
 * charge.
 * 
 * Commercial, government, and institutional users MUST register their
 * copies of XV, for the exceedingly REASONABLE price of just $25 per
 * workstation/X terminal.  Site licenses are available for those who
 * wish to run XV on a large number of machines.  Contact the author
 * for more details.
 *
 * The author may be contacted via:
 *    US Mail:  John Bradley
 *              1053 Floyd Terrace
 *              Bryn Mawr, PA  19010
 *
 *    Phone:    (215) 898-8813
 *    EMail:    bradley@cis.upenn.edu
 */


/*#include "xv.h"*/
#include <stdio.h>
#include <stdlib.h>
typedef char byte;
#define DEBUG 0
/* MONO returns total intensity of r,g,b components */
#define MONO(rd,gn,bl) (((rd)*11 + (gn)*16 + (bl)*5) >> 5)  /*.33R+ .5G+ .17B*/

#define PIC8 0
#define PIC24 1


typedef long int        count_int;

static int  Width, Height;
static int  curx, cury;
static long CountDown;
static int  Interlace;
static byte bw[2] = {0, 0xff};

#ifdef __STDC__
static void putword(int, FILE *);
static void compress(int, FILE *, const byte *, int);
static void output(int);
static void cl_block(void);
static void cl_hash(count_int);
static void char_init(void);
static void char_out(int);
static void flush_char(void);
#else
static void putword(), compress(), output(), cl_block(), cl_hash();
static void char_init(), char_out(), flush_char();
#endif

static byte pc2nc[256],r1[256],g1[256],b1[256];

extern byte *Conv24to8();

/*************************************************************/
int WriteGIF(FILE *fp,
			 byte *pic,
			 int ptype,			/* 0 for 8-bit, 1 for 24-bit */
			 int w, int h,
			 byte rmap[], byte gmap[], byte bmap[], int numcols,
			 int colorstyle, char *comment)
{
	int   RWidth, RHeight;
	int   LeftOfs, TopOfs;
	int   ColorMapSize, InitCodeSize, Background, BitsPerPixel;
	int   i,j,nc;
	byte *pic8;
	byte  rtemp[256],gtemp[256],btemp[256];

	if (ptype == PIC24) {  /* have to quantize down to 8 bits */
		/*fprintf(stdout,"WriteGIF: Calling Conv24to8\n");*/
		pic8 = Conv24to8(pic, w, h, 256, rtemp,gtemp,btemp);
		if (!pic8) {
			fprintf(stderr,"WriteGIF: Not enough memory for 24->8 bit conversion\n");
			return;
		}
		rmap = rtemp;  gmap = gtemp;  bmap = btemp;  numcols=256;
	} else
		pic8 = pic;

	/* if writing B/W stipple... */
	if (colorstyle==2) {
		rmap = gmap = bmap = bw;
		numcols = 2;
	}

	Interlace = 0;
	Background = 0;


	for (i=0; i<256; i++) { pc2nc[i] = r1[i] = g1[i] = b1[i] = 0; }

	/* compute number of unique colors */
	nc = 0;

	for (i=0; i<numcols; i++) {
		/* see if color #i is already used */
		for (j=0; j<i; j++) {
			if (rmap[i] == rmap[j] && gmap[i] == gmap[j] && 
				bmap[i] == bmap[j]) break;
		}

		if (j==i) {  /* wasn't found */
			pc2nc[i] = nc;
			r1[nc] = rmap[i];
			g1[nc] = gmap[i];
			b1[nc] = bmap[i];
			nc++;
		}
		else pc2nc[i] = pc2nc[j];
	}


	/* figure out 'BitsPerPixel' */
	for (i=1; i<8; i++)
		if ( (1<<i) >= nc) break;
  
	BitsPerPixel = i;

	ColorMapSize = 1 << BitsPerPixel;
	
	RWidth  = Width  = w;
	RHeight = Height = h;
	LeftOfs = TopOfs = 0;
	
	CountDown = w * h;    /* # of pixels we'll be doing */

	if (BitsPerPixel <= 1) InitCodeSize = 2;
	else InitCodeSize = BitsPerPixel;

	curx = cury = 0;

	if (!fp) {
		fprintf(stderr,  "WriteGIF: file not open for writing\n" );
		if (ptype == PIC24) free(pic8);
		return (1);
	}

	if (DEBUG) 
		fprintf(stderr,"WrGIF: pic=%x, w,h=%dx%d, numcols=%d, Bits%d,Cmap=%d\n",
				pic8, w,h,numcols,BitsPerPixel,ColorMapSize);

	if (comment && strlen(comment)>0)
		fwrite("GIF89a", 1, 6, fp);    /* the GIF magic number */
	else
		fwrite("GIF87a", 1, 6, fp);    /* the GIF magic number */

	putword(RWidth, fp);           /* screen descriptor */
	putword(RHeight, fp);

	i = 0x80;	                 /* Yes, there is a color map */
	i |= (8-1)<<4;                 /* OR in the color resolution (hardwired 8) */
	i |= (BitsPerPixel - 1);       /* OR in the # of bits per pixel */
	fputc(i,fp);          

	fputc(Background, fp);         /* background color */

	fputc(0, fp);                  /* future expansion byte */


	if (colorstyle == 1) {         /* greyscale */
		for (i=0; i<ColorMapSize; i++) {
			j = MONO(r1[i], g1[i], b1[i]);
			fputc(j, fp);
			fputc(j, fp);
			fputc(j, fp);
		}
	}
	else {
		for (i=0; i<ColorMapSize; i++) {       /* write out Global colormap */
			fputc(r1[i], fp);
			fputc(g1[i], fp);
			fputc(b1[i], fp);
		}
	}

	if (comment && strlen(comment)>0) {   /* write comment blocks */
		char *sp;
		int   i, blen;

		fputc(0x21, fp);     /* EXTENSION block */
		fputc(0xFE, fp);     /* comment extension */

		sp = comment;
		while ( (blen=strlen(sp)) > 0) {
			if (blen>255) blen = 255;
			fputc(blen, fp);
			for (i=0; i<blen; i++, sp++) fputc(*sp, fp);
		}
		fputc(0, fp);    /* zero-length data subblock to end extension */
	}


	fputc( ',', fp );              /* image separator */

	/* Write the Image header */
	putword(LeftOfs, fp);
	putword(TopOfs,  fp);
	putword(Width,   fp);
	putword(Height,  fp);
	if (Interlace) fputc(0x40, fp);   /* Use Global Colormap, maybe Interlace */
	else fputc(0x00, fp);

	fputc(InitCodeSize, fp);
	compress(InitCodeSize+1, fp, pic8, w*h);

	fputc(0,fp);                      /* Write out a Zero-length packet (EOF) */
	fputc(';',fp);                    /* Write GIF file terminator */
	if (ptype == PIC24) free(pic8);

	if (ferror(fp)) return -1;
	return (0);
}




/******************************/
static void putword(w, fp)
int w;
FILE *fp;
{
  /* writes a 16-bit integer in GIF order (LSB first) */
  fputc(w & 0xff, fp);
  fputc((w>>8)&0xff, fp);
}




/***********************************************************************/


static unsigned long cur_accum = 0;
static int           cur_bits = 0;




#define min(a,b)        ((a>b) ? b : a)

#define XV_BITS	12    /* BITS was already defined on some systems */
#define MSDOS	1

#define HSIZE  5003            /* 80% occupancy */

typedef unsigned char   char_type;


static int n_bits;                    /* number of bits/code */
static int maxbits = XV_BITS;         /* user settable max # bits/code */
static int maxcode;                   /* maximum code, given n_bits */
static int maxmaxcode = 1 << XV_BITS; /* NEVER generate this */

#define MAXCODE(n_bits)     ( (1 << (n_bits)) - 1)

static  count_int      htab [HSIZE];
static  unsigned short codetab [HSIZE];
#define HashTabOf(i)   htab[i]
#define CodeTabOf(i)   codetab[i]

static int hsize = HSIZE;            /* for dynamic table sizing */

/*
 * 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).
 */

#define tab_prefixof(i) CodeTabOf(i)
#define tab_suffixof(i)        ((char_type *)(htab))[i]
#define de_stack               ((char_type *)&tab_suffixof(1<<XV_BITS))

static int free_ent = 0;                  /* first unused entry */

/*
 * block compression parameters -- after all codes are used up,
 * and compression rate changes, start over.
 */
static int clear_flg = 0;

static long int in_count = 1;            /* length of input */
static long int out_count = 0;           /* # of codes output (for debugging) */

/*
 * 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 int g_init_bits;
static FILE *g_outfile;

static int ClearCode;
static int EOFCode;

static void xvbzero(char *s, int len) {
  for ( ; len>0; len--) *s++ = 0;
}

/********************************************************/
static void compress(int init_bits, FILE *outfile, const byte *data, int len)
{
  register long fcode;
  register int i = 0;
  register int c;
  register int ent;
  register int disp;
  register 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;

  /* initialize 'compress' globals */
  maxbits = XV_BITS;
  maxmaxcode = 1<<XV_BITS;
  xvbzero((char *) htab,    sizeof(htab));
  xvbzero((char *) codetab, sizeof(codetab));
  hsize = HSIZE;
  free_ent = 0;
  clear_flg = 0;
  in_count = 1;
  out_count = 0;
  cur_accum = 0;
  cur_bits = 0;


  /*
   * Set up the necessary values
   */
  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 = pc2nc[*data++];  len--;

  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(ClearCode);
    
  while (len) {
    c = pc2nc[*data++];  len--;
    in_count++;

    fcode = (long) ( ( (long) c << maxbits) + ent);
    i = (((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(ent);
    out_count++;
    ent = c;

    if ( free_ent < maxmaxcode ) {
      CodeTabOf (i) = free_ent++; /* code -> hashtable */
      HashTabOf (i) = fcode;
    }
    else
      cl_block();
  }

  /* Put out the final code */
  output(ent);
  out_count++;
  output(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
unsigned long masks[] = { 0x0000, 0x0001, 0x0003, 0x0007, 0x000F,
                                  0x001F, 0x003F, 0x007F, 0x00FF,
                                  0x01FF, 0x03FF, 0x07FF, 0x0FFF,
                                  0x1FFF, 0x3FFF, 0x7FFF, 0xFFFF };

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 );

#if 0
    if( ferror( g_outfile ) ) 
      FatalError("unable to write GIF file");
#endif
  }
}


/********************************/
static void cl_block ()             /* table clear for block compress */
{
  /* Clear out the hash table */

  cl_hash ( (count_int) hsize );
  free_ent = ClearCode + 2;
  clear_flg = 1;

  output(ClearCode);
}


/********************************/
static void cl_hash(hsize)          /* reset code table */
register count_int hsize;
{
  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'
 */
static int a_count;

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

/*
 * Define the storage for the packet accumulator
 */
static char accum[ 256 ];

/*
 * 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(c)
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;
  }
}