/**********************************************************************
 *	togif - 
 *		Convert an IRIS image to GIF format.  Converts b/w and 
 *	color images to 8 bit per pixel GIF format.  Color images
 *	are dithered with a 4 by 4 dither matrix.  GIF image files 
 *	may be uuencoded, and sent over the network.
 *
 *			Paul Haeberli @ Silicon Graphics - 1989
 *
 *    * Modified Jan 1995 - Made parallelizable via elimination of
 *    * global variables.
 **********************************************************************
 */
#include <stdio.h>
#include <string.h>
#include <math.h>
#include "togif.h"
#include <stdlib.h>
#define GIFGAMMA	(1.5)	/* smaller makes output image darker */
#define MAXCOLORS 256
#define CBITS    12

typedef int (* ifunptr)(int x,int y,vgl_GIFWriter *dataPtr);


/***************************************************************************
 * These routines interface the non-GIF data to the GIF black box (GIFENCOD)
 ***************************************************************************
 */
static int getgifpix2(int x,int y,vgl_GIFWriter *dataPtr);
static void getrow2(unsigned long *buffer,short *row,unsigned short width,
                    unsigned short rownum,unsigned short comp);
static void gammawarp(short *sbuf,float gam,int n,vgl_GIFWriter *dataPtr);
static short **makedittab(int levels,int mult,int add);
static int ditherrow(unsigned short *r,unsigned short *g,unsigned short *b,short *wp,
                     int n,int y,vgl_GIFWriter *dataPtr);

/******************************************************************************
 * GIF black box routines
 ******************************************************************************
 */
static void BumpPixel(vgl_GIFWriter *dataPtr);
static int GIFNextPixel(ifunptr getpixel,vgl_GIFWriter *dataPtr);
static int GIFEncode(FILE *fp,int GWidth,int GHeight,int GInterlace,int Background,
          int BitsPerPixel,int Red[],int Green[],int Blue[], ifunptr GetPixel,
          vgl_GIFWriter *dataPtr);
static void Putword(int w,FILE * fp );

/******************************************************************************
 * GIF compression black box routines
 ******************************************************************************
 */
static void compress(int init_bits,FILE *outfile,ifunptr ReadValue,vgl_GIFWriter *dataPtr );
static void output(code_int code,vgl_GIFWriter *dataPtr);
static void cl_block (vgl_GIFWriter *dataPtr);   
static void cl_hash(register count_int hsize,vgl_GIFWriter *dataPtr);
static void writeerr();
static void flush_char(vgl_GIFWriter *dataPtr);
static void char_out(int c,vgl_GIFWriter *dataPtr);
static void char_init(vgl_GIFWriter *dataPtr);

/************************ vgl_GIFWriterBegin() ******************************/
vgl_GIFWriter *vgl_GIFWriterBegin(void)
{
    vgl_GIFWriter *gifwriter;
    gifwriter = (vgl_GIFWriter *)G_malloc (sizeof(vgl_GIFWriter));
    return gifwriter;
}
/************************** vgl_GIFWriterEnd() ********************************/
void vgl_GIFWriterEnd(vgl_GIFWriter *gifwriter)
{
   G_free (gifwriter);
}
/********************** vgl_GIFWriterWriteGIFFile() ****************************/
void vgl_GIFWriterWriteGIFFile(vgl_GIFWriter *gifwriter,unsigned long *buffer,
                               int xsize, int ysize, int bwflag, FILE *outf)
{
    short r,g,b;
    int i;
    int bpp;
    int gifcolors;
    int rmap[MAXCOLORS];
    int gmap[MAXCOLORS];
    int bmap[MAXCOLORS];
    memset(gifwriter,'\0',sizeof(vgl_GIFWriter));
    gifwriter->maxbits = CBITS;                /* user settable max # bits/code */
    gifwriter->maxmaxcode = (code_int)1 << CBITS; /* should NEVER generate this code */
    gifwriter -> hsize = HSIZE;
    gifwriter -> in_count = 1;

    gifwriter -> xsize = xsize;
    gifwriter -> ysize = ysize;
    gifwriter->iscolor = !bwflag;
    gifwriter->buffer = buffer;
    if(gifwriter->iscolor) {
	gifcolors = 256;
	bpp = 8;
	for(i=0; i<gifcolors; i++) {
	   r = (i>>0)&0x7;
	   g = (i>>3)&0x7;
	   b = (i>>6)&0x3;
	   rmap[i] = (255*r)/7;
	   gmap[i] = (255*g)/7;
	   bmap[i] = (255*b)/3;
	}
    } else {
	gifcolors = 16;
	bpp = 4;
	for(i=0; i<gifcolors; i++) {
	   rmap[i] = (255*i)/(gifcolors-1);
	   gmap[i] = (255*i)/(gifcolors-1);
	   bmap[i] = (255*i)/(gifcolors-1);
	}
    }


    gifwriter->currow = -1;
    GIFEncode(outf,xsize,ysize,1,0,bpp,rmap,gmap,bmap,getgifpix2,gifwriter);

}
/************************** getgifpix2() ********************************/
static int getgifpix2(int x,int y,vgl_GIFWriter *dataPtr)
{
    int pix;

    if(dataPtr->iscolor) {
	if(dataPtr->currow!= y) {
	    getrow2(dataPtr->buffer,dataPtr->rbuf,dataPtr->xsize,dataPtr->ysize-1-y,0);
	    gammawarp(dataPtr->rbuf,1.0/GIFGAMMA,dataPtr->xsize,dataPtr);
	    getrow2(dataPtr->buffer,dataPtr->gbuf,dataPtr->xsize,dataPtr->ysize-1-y,1);
	    gammawarp(dataPtr->gbuf,1.0/GIFGAMMA,dataPtr->xsize,dataPtr);
	    getrow2(dataPtr->buffer,dataPtr->bbuf,dataPtr->xsize,dataPtr->ysize-1-y,2);
	    gammawarp(dataPtr->bbuf,1.0/GIFGAMMA,dataPtr->xsize,dataPtr);
	    ditherrow((unsigned short *)(dataPtr->rbuf),(unsigned short *)(dataPtr->gbuf),(unsigned short *)(dataPtr->bbuf),dataPtr->obuf,dataPtr->xsize,y,dataPtr);
	    dataPtr->currow = y;
	}
	pix = dataPtr->obuf[x];
    } else {
	if(dataPtr->currow != y) {
	    getrow2(dataPtr->buffer,dataPtr->rbuf,dataPtr->xsize,dataPtr->ysize-1-y,0);
	    gammawarp(dataPtr->rbuf,1.0/GIFGAMMA,dataPtr->xsize,dataPtr);
	    ditherrow((unsigned short *)(dataPtr->rbuf),(unsigned short *)(dataPtr->rbuf),(unsigned short *)(dataPtr->rbuf),dataPtr->obuf,dataPtr->xsize,y,dataPtr);
	    dataPtr->currow = y;
	}
	pix = dataPtr->obuf[x]&0xf;
    }
    return pix;
}
/************************** getrow2() ********************************/
static void getrow2(unsigned long *buffer,short *row,unsigned short width,unsigned short rownum,unsigned short comp)
{
   unsigned short i;
   unsigned long *ptr = buffer + width * rownum;
   switch(comp)
   {
      case 0:
        for(i = 0; i < width; i++)
        {
           row[i] = *ptr & 0xff;
           ptr++;
        }
        break;
      case 1:
        for(i = 0; i < width; i++)
        {
           row[i] = (*ptr>>8) & 0xff;
           ptr++;
        }
        break;
      case 2:
        for(i = 0; i < width; i++)
        {
           row[i] = (*ptr>>16) & 0xff;
           ptr++;
        }
        break;
   } 
}
/********************** gammawarp() ***************************/
static void gammawarp(short *sbuf,float gam,int n,vgl_GIFWriter *dataPtr)
{
    int i;
    float f;

    if(gam!=dataPtr->curgamma) {
	for(i=0; i<256; i++) 
	    dataPtr->gamtab[i] = 255*pow(i/255.0,gam)+0.5;
	dataPtr->curgamma = gam;
    }
    while(n--) {
	*sbuf = dataPtr->gamtab[*sbuf];
	sbuf++;
    }
}

/***************************************************************************
 *  	dithering code follows
 */
#define XSIZE	4
#define YSIZE	4
#define TOTAL		(XSIZE*YSIZE)
#define WRAPY(y)	((y)%YSIZE)
#define WRAPX(x)	((x)%XSIZE)

static short dithmat[YSIZE][XSIZE] = {
	0, 8, 2, 10,
	12, 4, 14, 6,
	3, 11, 1, 9,
	15, 7, 13, 5,
};

/************************** makedittab() ********************************/
static short **makedittab(int levels,int mult,int add)
{
    register int val;
    register int nshades;
    register int i, j, k;
    register int matval, tabval;
    short **tab;

    nshades = XSIZE*YSIZE*(levels-1)+1;
    tab = (short **)G_malloc (YSIZE*sizeof(short *));
    for(j=0; j<YSIZE; j++) {
	tab[j] = (short *)G_malloc (XSIZE*256*sizeof(short));
	for(i=0; i<XSIZE; i++ ) {
	    matval = dithmat[i][j]; 
	    for(k=0; k<256; k++) {
		val = (nshades*k)/255;
		if(val==nshades)
		    val = nshades-1;
		if((val%TOTAL)>matval) 
		    tabval =  (val/TOTAL)+1;
		else 
		    tabval = (val/TOTAL);
		tabval *= mult;
		tabval += add;
		tab[j][256*i+k] = tabval;
	    }
	}
    }
    return tab;
}
/************************** ditherrow() ********************************/
static int ditherrow(unsigned short *r,unsigned short *g,unsigned short *b,short *wp,
                     int n,int y,vgl_GIFWriter *dataPtr)
{
    short *rbase;
    short *gbase;
    short *bbase;

    if(!dataPtr->rtab) {
	if(dataPtr->iscolor) {
	    dataPtr->rtab = makedittab(8,1,0);
	    dataPtr->gtab = makedittab(8,8,0);
	    dataPtr->btab = makedittab(4,64,0);
	} else {
	    dataPtr->rtab = makedittab(16,1,0);
	    dataPtr->gtab = makedittab(2,16,0);
	    dataPtr->btab = makedittab(2,32,0);
	}
    }
    rbase = dataPtr->rtab[WRAPY(y)];
    gbase = dataPtr->gtab[WRAPY(y)];
    bbase = dataPtr->btab[WRAPY(y)];
    while(n) {
	if(n>=XSIZE) {
	    *wp++ = rbase[*r++ +   0] + gbase[*g++ +   0] + bbase[*b++ +   0];
	    *wp++ = rbase[*r++ + 256] + gbase[*g++ + 256] + bbase[*b++ + 256];
	    *wp++ = rbase[*r++ + 512] + gbase[*g++ + 512] + bbase[*b++ + 512];
	    *wp++ = rbase[*r++ + 768] + gbase[*g++ + 768] + bbase[*b++ + 768];
	    n -= XSIZE;
	} else {
	    *wp++ = rbase[*r++] + gbase[*g++] + bbase[*b++];
	    rbase += 256;
	    gbase += 256;
	    bbase += 256;
	    n--;
	}
    }
    return 1;
}


/*****************************************************************************
 * SCARY GIF code follows . . . . sorry.
 *
 * Based on GIFENCOD by David Rowley <mgardi@watdscu.waterloo.edu>.A
 * Lempel-Zim compression based on "compress".
 *
 *****************************************************************************
 */

/*****************************************************************************
 *
 * GIFENCODE.C    - GIF Image compression interface
 *
 * GIFEncode( FName, GHeight, GWidth, GInterlace, Background,
 *            BitsPerPixel, Red, Green, Blue, GetPixel )
 *
 *****************************************************************************/

#define TRUE 1
#define FALSE 0


/************************** BumpPixel() ********************************/
/*
 * Bump the 'curx' and 'cury' to point to the next pixel
 */
static void BumpPixel(vgl_GIFWriter *dataPtr)
{
    dataPtr->curx++;
    if( dataPtr->curx == dataPtr->xsize ) {
	dataPtr->curx = 0;
	if( !dataPtr->interlace ) {
	    dataPtr->cury++;
	} else {
	    switch( dataPtr->pass ) {
	     	case 0:
		    dataPtr->cury += 8;
		    if( dataPtr->cury >= dataPtr->ysize ) {
			dataPtr->pass++;
			dataPtr->cury = 4;
		    } 
		    break;
		case 1:
		    dataPtr->cury += 8;
		        if( dataPtr->cury >= dataPtr->ysize ) {
			    dataPtr->pass++;
			    dataPtr->cury = 2;
		      	}
		      	break;
	       	case 2:
		    dataPtr->cury += 4;
		    if( dataPtr->cury >= dataPtr->ysize ) {
		     	dataPtr->pass++;
			dataPtr->cury = 1;
		    }
		    break;
	       	case 3:
		    dataPtr->cury += 2;
		    break;
	    }
	}
    }
}

/************************** GIFNextPixel() ********************************/
/*
 * Return the next pixel from the image
 */
static int GIFNextPixel(ifunptr getpixel,vgl_GIFWriter *dataPtr )
{
    int r;

    if( dataPtr -> countDown == 0 )
	return EOF;
    dataPtr -> countDown--;
    r = (*getpixel)( dataPtr->curx, dataPtr->cury,dataPtr);
    BumpPixel(dataPtr);
    return r;
}

/************************** GIFEncode () ********************************/
/*
 * public GIFEncode
 */
static int GIFEncode(FILE *fp,int GWidth,int GHeight,int GInterlace,
          int Background,int BitsPerPixel,int Red[],int Green[],int Blue[], 
          ifunptr GetPixel,vgl_GIFWriter *dataPtr )
{
    int B;
    int RWidth, RHeight;
    int LeftOfs, TopOfs;
    int Resolution;
    int ColorMapSize;
    int InitCodeSize;
    int i;

    dataPtr->cur_bits = 0;

    dataPtr->interlace = GInterlace;
    ColorMapSize = 1 << BitsPerPixel;
    RWidth = dataPtr->xsize;
    RHeight = dataPtr->ysize;
    LeftOfs = TopOfs = 0;
    Resolution = BitsPerPixel;

    dataPtr->countDown = (long)(dataPtr->xsize) * (long)(dataPtr->ysize);
    dataPtr->pass = 0;
    if( BitsPerPixel <= 1 )
	InitCodeSize = 2;
    else
	InitCodeSize = BitsPerPixel;
    dataPtr->curx = dataPtr->cury = 0;
    fwrite( "GIF87a", 1, 6, fp );
    Putword( RWidth, fp );
    Putword( RHeight, fp );
    B = 0x80;       /* Yes, there is a color map */
    B |= (Resolution - 1) << 5;
    B |= (BitsPerPixel - 1);
    fputc( B, fp );
    fputc( Background, fp );
    fputc( 0, fp );
    for( i=0; i<ColorMapSize; i++ ) {
	fputc( Red[i], fp );
	fputc( Green[i], fp );
	fputc( Blue[i], fp );
    }
    fputc( ',', fp );
    Putword( LeftOfs, fp );
    Putword( TopOfs, fp );
    Putword( dataPtr->xsize, fp );
    Putword( dataPtr->ysize, fp );
    if( dataPtr->interlace )
	fputc( 0x40, fp );
    else
	fputc( 0x00, fp );
    fputc( InitCodeSize, fp );
    compress( InitCodeSize+1, fp, GetPixel,dataPtr );
    fputc( 0, fp );
    fputc( ';', fp );
    fclose( fp );
    return 1;
}

/************************** Putword () ********************************/
/*
 * 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 (mgardi@watdcsu.waterloo.edu)
 *
 ***************************************************************************/


/*
 *
 * 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)
 *
 */
#include <ctype.h>
#include <grass/gis.h>

#define ARGVAL() (*++(*argv) || (--argc && *++argv))

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

#define HashTabOf(i)    dataPtr->htab[i]
#define CodeTabOf(i)    dataPtr->codetab[i]


/*
 * 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**CBITS 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 *)(dataPtr->htab))[i]
#define de_stack               ((char_type *)&tab_suffixof((code_int)1<<CBITS))



/************************** compress () ********************************
 * 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,
                     vgl_GIFWriter *dataPtr )
{
    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
     */
    dataPtr->g_init_bits = init_bits;
    dataPtr->g_outfile = outfile;
    /*
     * Set up the necessary values
     */
    dataPtr->offset = 0;
    dataPtr->out_count = 0;
    dataPtr->clear_flg = 0;
    dataPtr->in_count = 1;
    dataPtr->maxcode = MAXCODE(dataPtr->n_bits = dataPtr->g_init_bits);
    dataPtr->clearCode = (1 << (init_bits - 1));
    dataPtr->EOFCode = dataPtr->clearCode + 1;
    dataPtr->free_ent = dataPtr->clearCode + 2;
    char_init(dataPtr);
    ent = GIFNextPixel( ReadValue,dataPtr );
    hshift = 0;
    for ( fcode = (long) (dataPtr->hsize);  fcode < 65536L; fcode *= 2L )
        hshift++;
    hshift = 8 - hshift;                /* set hash code range bound */
    hsize_reg = dataPtr->hsize;
    cl_hash( (count_int) hsize_reg,dataPtr);            /* clear hash table */
    output( (code_int)(dataPtr->clearCode),dataPtr );
    while ( (c = GIFNextPixel( ReadValue,dataPtr)) != EOF ) {
        dataPtr->in_count++;
        fcode = (long) (((long) c << dataPtr->maxbits) + ent);
        /* i = (((code_int)c << hshift) ~ 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,dataPtr );
        dataPtr->out_count++;
        ent = c;
        if ( dataPtr->free_ent < dataPtr->maxmaxcode ) {
            CodeTabOf (i) = dataPtr->free_ent++; /* code -> hashtable */
            HashTabOf (i) = fcode;
        } else
                cl_block(dataPtr);
    }
    /*
     * Put out the final code.
     */
    output( (code_int)ent,dataPtr );
    dataPtr->out_count++;
    output( (code_int) (dataPtr->EOFCode),dataPtr );
    return;
}

/*****************************************************************
 * 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 CBITS 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,vgl_GIFWriter *dataPtr )
{
    dataPtr->cur_accum &= masks[ dataPtr->cur_bits ];
    if( dataPtr->cur_bits > 0 )
        dataPtr->cur_accum |= ((long)code << dataPtr->cur_bits);
    else
        dataPtr->cur_accum = code;
    dataPtr->cur_bits += dataPtr->n_bits;
    while( dataPtr->cur_bits >= 8 ) {
        char_out( (unsigned int)(dataPtr->cur_accum & 0xff),dataPtr );
        dataPtr->cur_accum >>= 8;
        dataPtr->cur_bits -= 8;
    }

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

/********************** cl_block() ***************************/
/*
 * table clear for block compress
 */
static void cl_block (vgl_GIFWriter *dataPtr)   
{
        cl_hash ( (count_int)(dataPtr->hsize),dataPtr);
        dataPtr->free_ent = dataPtr->clearCode + 2;
        dataPtr->clear_flg = 1;
        output( (code_int)(dataPtr->clearCode),dataPtr );
}

/********************** cl_hash() ***************************/
/* reset code table */
static void cl_hash(register count_int hsize,vgl_GIFWriter *dataPtr)    
{
        register count_int *htab_p;
        register long i;
        register long m1 = -1;
        htab_p = dataPtr->htab+hsize;

        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;
}

/********************** writeerr() ***************************/
static void writeerr()
{
}

/******************************************************************************
 *
 * GIF Specific routines used by compression stuff
 *
 ******************************************************************************/

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

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

/********************** char_out() ***************************/
/*
 * 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,vgl_GIFWriter *dataPtr)
{
        dataPtr->accum[ dataPtr->a_count++ ] = c;
        if( dataPtr->a_count >= 254 )
                flush_char(dataPtr);
}

/********************** flush_char() ***************************/
/*
 * Flush the packet to disk, and reset the accumulator
 */
static void flush_char(vgl_GIFWriter *dataPtr)
{
        if( dataPtr->a_count > 0 ) {
                fputc( dataPtr->a_count, dataPtr->g_outfile );
                fwrite( dataPtr->accum, 1, dataPtr->a_count, dataPtr->g_outfile );
                dataPtr->a_count = 0;
        }
}
/*
main(int argc,char *argv[] )
{
    FILE *of;
    int xsize, ysize,bwflag;
    unsigned long *buffer;
    int i;
    int j;
    vgl_GIFWriter *gifwriter;

    if(argc<3) {
	fprintf(stderr,"usage: togif image.rgb image.gif\n");
	exit(1);
    }
    gifwriter = vgl_GIFWriterBegin();

    xsize = ysize = 200;
    buffer = (unsigned long *)G_malloc ((xsize)*(ysize) * sizeof(unsigned long));
    for(i = 0; i < ysize; i++)
    {
       for(j = 0; j < xsize; j++)
       {
           
         
           buffer[j + i * xsize] =
              i | j << 8 | (0xff<<24);
       }
                   
    }
    bwflag = 0;

    of = fopen(argv[2],"w");
    if(!of) {
	fprintf(stderr,"togif: can't open output image [%s]\n",argv[2]);
	exit(1);
    }
    vgl_GIFWriterWriteGIFFile(gifwriter,buffer,xsize,ysize,bwflag,of);
    vgl_GIFWriterEnd(gifwriter);
    fclose(of);
    exit(0);
}
*/

