/* +-------------------------------------------------------------------+ */
/* | Copyright 1993, David Koblas (koblas@netcom.com)                  | */
/* |                                                                   | */
/* | Permission to use, copy, modify, and to distribute this software  | */
/* | and its documentation for any purpose is hereby granted without   | */
/* | fee, provided that the above copyright notice appear in all       | */
/* | copies and that both that copyright notice and this permission    | */
/* | notice appear in supporting documentation.  There is no           | */
/* | representations about the suitability of this software for        | */
/* | any purpose.  this software is provided "as is" without express   | */
/* | or implied warranty.                                              | */
/* |                                                                   | */
/* +-------------------------------------------------------------------+ */

/* $Id: writeGIF.c,v 1.8 1996/09/06 06:59:49 torsten Exp $ */

/* ppmtogif.c - read a portable pixmap and produce a GIF file
**
** Based on GIFENCOD by David Rowley <mgardi@watdscu.waterloo.edu>.A
** Lempel-Ziv compression based on "compress".
**
** Copyright (C) 1989 by Jef Poskanzer.
**
** Permission to use, copy, modify, and distribute this software and its
** documentation for any purpose and without fee is hereby granted, provided
** that the above copyright notice appear in all copies and that both that
** copyright notice and this permission notice appear in supporting
** documentation.  This software is provided "as is" without express or
** implied warranty.
**
** The Graphics Interchange Format(c) is the Copyright property of
** CompuServe Incorporated.  GIF(sm) is a Service Mark property of
** CompuServe Incorporated.
 */

#include <stdio.h>
#include "image.h"
#include "rwTable.h"

#define MAXCOLORS 256

/*
 * Pointer to function returning an int
 */
typedef int (*ifunptr) (int, int);

/*
 * a code_int must be able to hold 2**BITS values of type int, and also -1
 */
typedef int code_int;

#ifdef SIGNED_COMPARE_SLOW
typedef unsigned long int count_int;
typedef unsigned short int count_short;
#else				/*SIGNED_COMPARE_SLOW */
typedef long int count_int;
#endif				/*SIGNED_COMPARE_SLOW */

static int colorstobpp(int colors);
static int GetPixel(int x, int y);
static void BumpPixel(void);
static int GIFNextPixel(ifunptr getpixel);
static void GIFEncode(FILE * fp, int GWidth, int GHeight,
		      int GInterlace, int Background, int BitsPerPixel,
		      int Red[], int Green[], int Blue[], ifunptr GetPixel);
static void Putword(int w, FILE * fp);
static void compress(int init_bits, FILE * outfile, ifunptr ReadValue);
static void output(code_int code);
static void cl_block(void);
static void cl_hash(count_int hsize);
static void char_init(void);
static void char_out(int c);
static void flush_char(void);

static Image *image;

int
WriteGIF(char *file, Image * outImage)
{
    extern int errno;
    int r[MAXCOLORS], g[MAXCOLORS], b[MAXCOLORS];
    int i, bpp;
    FILE *fp;

    errno = 0;
    fp = fopen(file, "w");
    if (fp == NULL)
	return 1;

    image = ImageCompress(outImage, MAXCOLORS, 0);

    bpp = colorstobpp(image->cmapSize);

    for (i = 0; i < image->cmapSize; i++) {
	r[i] = image->cmapData[i * 3 + 0];
	g[i] = image->cmapData[i * 3 + 1];
	b[i] = image->cmapData[i * 3 + 2];
    }
    for (; i < MAXCOLORS; i++)
	r[i] = g[i] = b[i] = 0;

    GIFEncode(fp, image->width, image->height, 0, 0, bpp, r, g, b, GetPixel);
    fclose(fp);

    ImageDelete(image);

    if (errno) {
	RWSetMsg("Out of space");
	return 1;
    }
    
    return 0;
}

static int
colorstobpp(int colors)
{
    int bpp;

    if (colors <= 2)
	bpp = 1;
    else if (colors <= 4)
	bpp = 2;
    else if (colors <= 8)
	bpp = 3;
    else if (colors <= 16)
	bpp = 4;
    else if (colors <= 32)
	bpp = 5;
    else if (colors <= 64)
	bpp = 6;
    else if (colors <= 128)
	bpp = 7;
    else
	bpp = 8;

    return bpp;
}

static int
GetPixel(int x, int y)
{
    return image->data[x + y * image->width];
}


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

#define TRUE 1
#define FALSE 0

static int Width, Height;
static int curx, cury;
static long CountDown;
static int Pass;
static int Interlace;

/*
 * Bump the 'curx' and 'cury' to point to the next pixel
 */
static void BumpPixel()
{
    /*
     * Bump the current X position
     */
    ++curx;

    /*
     * If we are at the end of a scan line, set curx back to the beginning
     * If we are interlaced, bump the cury to the appropriate spot,
     * otherwise, just increment it.
     */
    if (curx == Width) {
	curx = 0;

	if (!Interlace)
	    ++cury;
	else {
	    switch (Pass) {
	    case 0:
		cury += 8;
		if (cury >= Height) {
		    ++Pass;
		    cury = 4;
		}
		break;

	    case 1:
		cury += 8;
		if (cury >= Height) {
		    ++Pass;
		    cury = 2;
		}
		break;

	    case 2:
		cury += 4;
		if (cury >= Height) {
		    ++Pass;
		    cury = 1;
		}
		break;

	    case 3:
		cury += 2;
		break;
	    }
	}
    }
}

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

    if (CountDown == 0)
	return EOF;

    --CountDown;

    r = (*getpixel) (curx, cury);

    BumpPixel();

    return r;
}

static void
GIFEncode(FILE * fp, int GWidth, int GHeight, int GInterlace, 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
     */
    if (fwrite("GIF87a", 1, 6, fp) != 6) {
	RWSetMsg("Error writing GIF header");
	fclose(fp);
	return;
    }

    /*
     * Write out the screen width and height
     */
    Putword(RWidth, fp);
    Putword(RHeight, fp);

    /*
     * Flag: global colour map, resolution, bits per pixel
     */
    B = 0x80 | (Resolution - 1) << 5 | (BitsPerPixel - 1);

    /*
     * Write the flag, the background colour and a byte of 0's (future expansion)
     */
    fputc(B, fp);
    fputc(Background, fp);
    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
     */
    fputc(Interlace ? 0x40 : 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);
}

/*
 * 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)
 *
 ***************************************************************************/

/*
 * General DEFINEs
 */

#define BITS    12

#define HSIZE  5003		/* 80% occupancy */

#ifdef NO_UCHAR
typedef char char_type;
#else				/*NO_UCHAR */
typedef unsigned char char_type;
#endif				/*NO_UCHAR */

/*
 * 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>

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

static int n_bits;		/* number of bits/code */
static int maxbits;		/* user settable max # bits/code */
static code_int maxcode;	/* maximum code, given n_bits */
static code_int maxmaxcode;	/* should NEVER generate this code */
#define MAXCODE(n_bits)        	(((code_int) 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 code_int hsize;		/* for dynamic table sizing */

static unsigned long cur_accum;
static int cur_bits;

/*
 * 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((code_int)1<<BITS))

static code_int free_ent;	/* first unused entry */

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

static int offset;
static long int in_count;	/* length of input */
static long int out_count;	/* # 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
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;
    maxbits = BITS;
    maxmaxcode = 1 << BITS;
    maxcode = MAXCODE(n_bits = g_init_bits);
    hsize = HSIZE;
    cur_accum = 0;
    cur_bits = 0;

    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 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);
    }
}

/*
 * Clear out the hash table
 */
static void
cl_block(void)
{				/* 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'
 */
static int a_count;

/*
 * Set up the 'byte output' routine
 */
static void
char_init(void)
{
    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(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(void)
{
    if (a_count > 0) {
	fputc(a_count, g_outfile);
	fwrite(accum, 1, a_count, g_outfile);
	a_count = 0;
    }
}

/* The End */