gimp/plug-ins/common/gif.c

/* GIF saving file filter for The GIMP version 1.0/1.1
 *
 *    - Adam D. Moss
 *    - Peter Mattis
 *    - Spencer Kimball
 *
 *      Based around original GIF code by David Koblas.
 *
 *
 * Version 3.0.2 - 99/04/25
 *                        Adam D. Moss - <adam@gimp.org> <adam@foxbox.org>
 */
/*
 * This filter uses code taken from the "giftopnm" and "ppmtogif" programs
 *    which are part of the "netpbm" package.
 */
/*
 *  "The Graphics Interchange Format(c) is the Copyright property of
 *  CompuServe Incorporated.  GIF(sm) is a Service Mark property of
 *  CompuServe Incorporated." 
 */

/*
 * REVISION HISTORY
 *
 * 99/04/25
 * 3.00.02 - Save the comment back onto the image as a persistent
 *           parasite if the comment was edited.
 *
 * 99/03/30
 * 3.00.01 - Round image timing to nearest 10ms instead of
 *           truncating.  Insert a mandatory 10ms minimum delay
 *           for the frames of looping animated GIFs, to avoid
 *           generating an evil CPU-sucking animation that 'other'
 *           GIF-animators sometimes like to save.
 *
 * 99/03/20
 * 3.00.00 - GIF-loading code moved to separate plugin.
 *
 * 99/02/22
 * 2.01.02 - Don't show a progress bar when loading non-interactively
 *
 * 99/01/23
 * 2.01.01 - Use a text-box to permit multi-line comments.  Don't
 *           try to write comment blocks which are longer than
 *           permitted.
 *
 * 98/10/09
 * 2.01.00 - Added support for persistent GIF Comments through
 *           the GIMP 1.1 GimpParasite mechanism where available.
 *           Did some user-interface tweaks.
 *           Fixed a bug when trying to save a GIF smaller
 *           than five pixels high as interlaced.
 *
 * 98/09/28
 * 2.00.05 - Fixed TigerT's Infinite GIF Bug.  Icky one.
 *
 * 98/09/15
 * 2.00.04 - The facility to specify the background colour of
 *           a transparent/animated GIF for non-transparent
 *           viewers now works very much more consistantly.
 *
 *           The only situations in which it will fail to work
 *           as expected now are those where file size can be reduced
 *           (abeit not by much, as the plugin is sometimes more pessimistic
 *           than it need be) by re-using an existing unused colour
 *           index rather than using another bit per pixel in the
 *           encoded file.  That will never be an issue with an image
 *           which was freshly converted from RGB to INDEXED with the
 *           Quantize option, as that option removes any unused colours
 *           from the image.
 *
 *           Let me know if you find the consistancy/size tradeoff more
 *           annoying than helpful and I can adjust it.  IMHO it is too
 *           arcane a feature to present to any user as a runtime option.
 *
 * 98/05/18
 * 2.00.03 - If we did manage to decode at least one frame of a
 *           gif, be sure to display the resulting image even if
 *           it terminated abruptly.
 *
 * 98/04/28
 * 2.00.02 - Fixed a bug with (ms) tag parsing.
 *
 * 98/03/16
 * 2.00.01 - Fixed a long-standing bug when loading GIFs which layer
 *           opaque frames onto transparent ones.
 *
 * 98/03/15
 * 2.00.00 - No longer beta.  Uses the current GIMP brush background
 *           colour as the transparent-index colour for viewers that
 *           don't know about transparency, instead of magenta.  Note
 *           that this is by no means likely to actually work, but
 *           is more likely to do so if your image has been freshly
 *           to-index'd before saving.
 *
 *           Also added some analysis to gif-reading to prevent the
 *           number of encoded bits being pumped up inadvertantly for
 *           successive load/saves of the same image.  [Adam]
 *
 * 97/12/11
 * 1.99.18 - Bleh.  Disposals should specify how the next frame will
 *           be composed with this frame, NOT how this frame will
 *           be composed with the previous frame.  Fixed.  [Adam]
 *
 * 97/11/30
 * 1.99.17 - No more bogus transparency indices in animated GIFs,
 *           hopefully.  Saved files are better-behaved, sometimes
 *           smaller.  [Adam]
 *
 * 97/09/29
 * 1.99.16 - Added a dialog for the user to choose what to do if
 *           one of the layers of the image extends beyond the image
 *           borders - crop or cancel.  Added code behind it.
 *
 *           Corrected the number of bits for the base image to be
 *           on the generous side.  Hopefully we can no longer generate
 *           GIFs which make XV barf.
 *
 *           Now a lot more careful about whether we choose to encode
 *           as a GIF87a or a GIF89a.  Hopefully does everything by the
 *           book.  It should now be nigh-on impossible to torture the
 *           plugin into generating a GIF which isn't extremely well
 *           behaved with respect to the GIF89a specification.
 *
 *           Fixed(?) a lot of dialog callback details, should now be
 *           happy with window deletion (GTK+970925).  Fixed the
 *           cancellation of a save.  [Adam]
 *
 * 97/09/16
 * 1.99.15 - Hey!  We can now cope with loading images which change
 *           colourmap between frames.  This plugin will never save
 *           such abominations of nature while I still live, though.
 *           There should be no noncorrupt GIF in the universe which
 *           GIMP can't load and play now.  [Adam]
 *
 * 97/09/14
 * 1.99.14 - Added a check for layers whose extents don't lay
 *           within the image boundaries, which would make it a
 *           lot harder to generate badly-behaved GIFs.  Doesn't
 *           do anything about it yet, but it should crop all layers
 *           to the image boundaries.  Also, there's now a (separate)
 *           animation-preview plugin!  [Adam]
 *
 * 97/08/29
 * 1.99.13 - Basic ability to embed GIF comments within saved images.
 *           Fixed a bug with encoding the number of loops in a GIF file -
 *           would have been important, but we're not using that feature
 *           yet anyway.  ;)
 *           Subtly improved dialog layout a little. [Adam]
 *
 * 97/07/25
 * 1.99.12 - Fixed attempts to load GIFs which don't exist.  Made a
 *           related cosmetic adjustment. [Adam]
 *
 * 97/07/10
 * 1.99.11 - Fixed a bug with loading and saving GIFs where the bottom
 *           layer wasn't the same size as the image. [Adam]
 *
 * 97/07/06
 * 1.99.10 - New 'save' dialog, now most of the default behaviour of
 *           animated GIF saving is user-settable (looping, default
 *           time between frames, etc.)
 *           PDB entry for saving is no longer compatible.  Fortunately
 *           I don't think that anyone is using file_gif_save in
 *           scripts.  [Adam]
 *
 * 97/07/05
 * 1.99.9  - More animated GIF work: now loads and saves frame disposal
 *           information.  This is neat and will also allow some delta
 *           stuff in the future.
 *           The disposal-method is kept in the layer name, like the timing
 *           info.
 *           (replace) - this frame replaces whatever else has been shown
 *                       so far.
 *           (combine) - this frame builds apon the previous frame.
 *           If a disposal method is not specified, it is assumed to mean
 *           "don't care."  [Adam]
 *
 * 97/07/04
 * 1.99.8  - Can save per-frame timing information too, now.  The time
 *           for which a frame is visible is specified within the layer name
 *           as i,e. (250ms).  If a frame doesn't have this timing value
 *           it defaults to lasting 100ms. [Adam]
 *
 * 97/07/02
 * 1.99.7  - For animated GIFs, fixed the saving of timing information for
 *           frames which couldn't be made transparent.
 *           Added the loading of timing information into the layer
 *           names.  Adjusted GIMP's GIF magic number very slightly. [Adam]
 *
 * 97/06/30
 * 1.99.6  - Now saves GRAY and GRAYA images, albeit not always
 *           optimally (yet). [Adam]
 *
 * 97/06/25
 * 1.99.5  - Good, the transparancy-on-big-architectures bug is
 *           fixed.  Cleaned up some stuff.
 *           (Adam D. Moss, adam@foxbox.org)
 *
 * 97/06/23
 * 1.99.4  - Trying to fix some endianness/word-size problems with
 *           transparent gif-saving on some architectures... does
 *           this help?  (Adam D. Moss, adam@foxbox.org)
 *
 * 97/05/18
 * 1.99.3  - Fixed the problem with GIFs getting loop extensions even
 *           if they only had one frame (thanks to Zach for noticing -
 *           git!  :) )  (Adam D. Moss, adam@foxbox.org)
 *
 * 97/05/17
 * 1.99.2  - Can now save animated GIFs.  Correctly handles saving of
 *           image offsets.  Uses N*tscape extentions to loop infinitely.
 *           Some notable shortcomings - see TODO list below.
 *           (Adam D. Moss, adam@foxbox.org)
 *
 * 97/05/16
 * 1.99.1  - Implemented image offsets in animated GIF loading.  Requires
 *           a fix to gimp_layer_translate in libgimp/gimplayer.c if used
 *           with GIMP versions <= 0.99.10.  Started work on saving animated
 *           GIFs.  Started TODO list.  (Adam D. Moss, adam@foxbox.org)
 *
 * 97/05/15
 * 1.99.0  - Started revision log.  GIF plugin now loads/saves INDEXED
 *           and INDEXEDA images with correct transparency where possible.
 *           Loads multi-image (animated) GIFs as a framestack implemented
 *           in GIMP layers.  Some bug fixes to original code, some new bugs
 *           cheerfully added.  (Adam D. Moss, adam@foxbox.org)
 *
 * Previous versions - load/save INDEXED images.
 *           (Peter Mattis & Spencer Kimball, gimp@scam.xcf.berkeley.edu)
 */

/*
 * TODO (more *'s means more important!)
 *
 * - PDB stuff for comments
 *
 * - 'requantize' option for INDEXEDA images which really have 256 colours
 *   in them
 *
 * - Be a bit smarter about finding unused/superfluous colour indices for
 *   lossless colour crunching of INDEXEDA images.  (Specifically, look
 *   for multiple indices which correspond to the same physical colour.)
 *
 * - Tidy up parameters for the GIFEncode routines
 *
 * - Remove unused colourmap entries for GRAYSCALE images.
 *
 * - Button to activate the animation preview plugin from the GIF-save
 *   dialog.
 *
 */

/* Copyright notice for code which this plugin was long ago derived from */
/* +-------------------------------------------------------------------+ */
/* | Copyright 1990, 1991, 1993, David Koblas.  (koblas@netcom.com)    | */
/* |   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.           | */
/* +-------------------------------------------------------------------+ */

#include "config.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>

#include <libgimp/gimp.h>
#include <libgimp/gimpui.h>

#include "libgimp/stdplugins-intl.h"


/* uncomment the line below for a little debugging info */
/* #define GIFDEBUG yesplease */

/* Does the version of GIMP we're compiling for support
   data attachments to images?  ('Parasites') */
#ifdef GIMP_HAVE_PARASITES
#define FACEHUGGERS aieee
#endif
/* PS: I know that technically facehuggers aren't parasites,
   the pupal-forms are.  But facehuggers are ky00te. */

enum
{
  DISPOSE_UNSPECIFIED,
  DISPOSE_COMBINE,
  DISPOSE_REPLACE
};

typedef struct
{
  gint interlace;
  gint save_comment;
  gint loop;
  gint default_delay;
  gint default_dispose;
} GIFSaveVals;

typedef struct
{
  gint run;
} GIFSaveInterface;



/* Declare some local functions.
 */
static void   query                    (void);
static void   run                      (gchar   *name,
					gint     nparams,
					GimpParam  *param,
					gint    *nreturn_vals,
					GimpParam **return_vals);
static gint   save_image               (gchar   *filename,
					gint32   image_ID,
					gint32   drawable_ID,
					gint32   orig_image_ID);

static gboolean boundscheck            (gint32 image_ID);
static gboolean badbounds_dialog       (void);

static void   cropok_callback          (GtkWidget *widget, gpointer   data);

static gint   save_dialog              (gint32 image_ID);

static void   save_ok_callback         (GtkWidget *widget, gpointer   data);
static void   comment_entry_callback   (GtkWidget *widget, gpointer   data);


static gboolean comment_was_edited = FALSE;

static gboolean can_crop = FALSE;
static GimpRunModeType run_mode;
#ifdef FACEHUGGERS
GimpParasite * comment_parasite = NULL;
#endif

/* For compression code */
static gint Interlace;


GimpPlugInInfo PLUG_IN_INFO =
{
  NULL,  /* init_proc  */
  NULL,  /* quit_proc  */
  query, /* query_proc */
  run,   /* run_proc   */
};

static GIFSaveVals gsvals =
{
  FALSE,   /* interlace                            */
  TRUE,    /* save comment                         */
  TRUE,    /* loop infinitely                      */
  100,     /* default_delay between frames (100ms) */
  0        /* default_dispose = "don't care"       */
};

static GIFSaveInterface gsint =
{
  FALSE   /*  run  */
};


MAIN ()

static void
query (void)
{
  static GimpParamDef save_args[] =
  {
    { GIMP_PDB_INT32,    "run_mode",        "Interactive, non-interactive" },
    { GIMP_PDB_IMAGE,    "image",           "Image to save" },
    { GIMP_PDB_DRAWABLE, "drawable",        "Drawable to save" },
    { GIMP_PDB_STRING,   "filename",        "The name of the file to save the image in" },
    { GIMP_PDB_STRING,   "raw_filename",    "The name entered" },
    { GIMP_PDB_INT32,    "interlace",       "Try to save as interlaced" },
    { GIMP_PDB_INT32,    "loop",            "(animated gif) loop infinitely" },
    { GIMP_PDB_INT32,    "default_delay",   "(animated gif) Default delay between framese in milliseconds" },
    { GIMP_PDB_INT32,    "default_dispose", "(animated gif) Default disposal type (0=`don't care`, 1=combine, 2=replace)" }
  };
  static gint nsave_args = sizeof (save_args) / sizeof (save_args[0]);

  gimp_install_procedure ("file_gif_save",
                          "saves files in Compuserve GIF file format",
                          "FIXME: write help for gif_save",
                          "Spencer Kimball, Peter Mattis, Adam Moss, David Koblas",
                          "Spencer Kimball, Peter Mattis, Adam Moss, David Koblas",
                          "1995-1997",
                          "<Save>/GIF",
			  "INDEXED*, GRAY*",
                          GIMP_PLUGIN,
                          nsave_args, 0,
                          save_args, NULL);

  gimp_register_save_handler ("file_gif_save",
			      "gif",
			      "");
}

static void
run (gchar   *name,
     gint     nparams,
     GimpParam  *param,
     gint    *nreturn_vals,
     GimpParam **return_vals)
{
  static GimpParam values[2];
  GimpPDBStatusType   status = GIMP_PDB_SUCCESS;
  gint32        image_ID;
  gint32        drawable_ID;
  gint32        orig_image_ID;
  GimpExportReturnType export = GIMP_EXPORT_CANCEL;

  run_mode = param[0].data.d_int32;

  *nreturn_vals = 1;
  *return_vals  = values;
  values[0].type          = GIMP_PDB_STATUS;
  values[0].data.d_status = GIMP_PDB_EXECUTION_ERROR;

  if (strcmp (name, "file_gif_save") == 0)
    {
      INIT_I18N_UI();
      gimp_ui_init ("gif", FALSE);

      image_ID    = orig_image_ID = param[1].data.d_int32;
      drawable_ID = param[2].data.d_int32;

      /*  eventually export the image */ 
      switch (run_mode)
	{
	case GIMP_RUN_INTERACTIVE:
	case GIMP_RUN_WITH_LAST_VALS:
	  export = gimp_export_image (&image_ID, &drawable_ID, "GIF", 
				      (GIMP_EXPORT_CAN_HANDLE_INDEXED |
				       GIMP_EXPORT_CAN_HANDLE_GRAY | 
				       GIMP_EXPORT_CAN_HANDLE_ALPHA  |
				       GIMP_EXPORT_CAN_HANDLE_LAYERS_AS_ANIMATION));
	  if (export == GIMP_EXPORT_CANCEL)
	    {
	      values[0].data.d_status = GIMP_PDB_CANCEL;
	      return;
	    }
	  break;
	default:
	  break;
	}

      if (boundscheck (image_ID))
	/* The image may or may not have had layers out of
	   bounds, but the user didn't mind cropping it down. */
	{
	  switch (run_mode)
	    {
	    case GIMP_RUN_INTERACTIVE:
	      /*  Possibly retrieve data  */
	      gimp_get_data ("file_gif_save", &gsvals);
		
	      /*  First acquire information with a dialog  */
	      if (! save_dialog (image_ID))
		status = GIMP_PDB_CANCEL;
	      break;
	      
	    case GIMP_RUN_NONINTERACTIVE:
	      /*  Make sure all the arguments are there!  */
	      if (nparams != 9)
		{
		  status = GIMP_PDB_CALLING_ERROR;
		}
	      else
		{
		  gsvals.interlace       = (param[5].data.d_int32) ? TRUE : FALSE;
		  gsvals.save_comment    = TRUE;  /*  no way to to specify that through the PDB  */
		  gsvals.loop            = (param[6].data.d_int32) ? TRUE : FALSE;
		  gsvals.default_delay   = param[7].data.d_int32;
		  gsvals.default_dispose = param[8].data.d_int32;
		}
	      break;
	      
	    case GIMP_RUN_WITH_LAST_VALS:
	      /*  Possibly retrieve data  */
	      gimp_get_data ("file_gif_save", &gsvals);
	      break;
	      
	    default:
	      break;
	    }

	  if (status == GIMP_PDB_SUCCESS)
	    {
	      if (save_image (param[3].data.d_string,
			      image_ID,
			      drawable_ID,
			      orig_image_ID))
		{
		  /*  Store psvals data  */
		  gimp_set_data ("file_gif_save", &gsvals, sizeof (GIFSaveVals));
		}
	      else
		{
		  status = GIMP_PDB_EXECUTION_ERROR;
		}
	    }
	}
      else /* Some layers were out of bounds and the user wishes
	      to abort.  */
	{
	  status = GIMP_PDB_CANCEL;
	}

      if (export == GIMP_EXPORT_EXPORT)
	gimp_image_delete (image_ID);
    }

  values[0].data.d_status = status;
}

#define MAXCOLORMAPSIZE  256

#define INTERLACE          0x40
#define LOCALCOLORMAP      0x80

#define GRAYSCALE        1
#define COLOR            2

typedef guchar CMap[3][MAXCOLORMAPSIZE];


gint   verbose = FALSE;
gchar *globalcomment = NULL;



/* 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".
**
** Modified by Marcel Wijkstra <wijkstra@fwi.uva.nl>
**
**
** 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.
*/

#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 find_unused_ia_colour (guchar *pixels,
				  int numpixels,
				  int num_indices,
				  int* colors);

void special_flatten_indexed_alpha (guchar *pixels,
				    int *transparent,
				    int *colors,
				    int numpixels);
static int colorstobpp (int);
static int bpptocolors (int);
static int GetPixel (int, int);
static void BumpPixel (void);
static int GIFNextPixel (ifunptr);

static void GIFEncodeHeader (FILE *, gboolean, int, int, int, int,
			     int *, int *, int *, ifunptr);
static void GIFEncodeGraphicControlExt (FILE *, int, int, int, int, int,
					int, int, int, int *, int *, int *,
					ifunptr);
static void GIFEncodeImageData (FILE *, int, int, int, int, int, int,
				int *, int *, int *, ifunptr, gint, gint);
static void GIFEncodeClose (FILE *, int, int, int, int, int, int,
			    int *, int *, int *, ifunptr);
static void GIFEncodeLoopExt (FILE *, guint);
static void GIFEncodeCommentExt (FILE *, char *);

int rowstride;
guchar *pixels;
int cur_progress;
int max_progress;

static void Putword (int, FILE *);
static void compress (int, FILE *, ifunptr);
static void output (code_int);
static void cl_block (void);
static void cl_hash (count_int);
static void writeerr (void);
static void char_init (void);
static void char_out (int);
static void flush_char (void);



static int find_unused_ia_colour (guchar *pixels,
				  int numpixels,
				  int num_indices,
				  int* colors)
{
  int i;
  gboolean ix_used[256];

#ifdef GIFDEBUG
  g_print ("GIF: fuiac: Image claims to use %d/%d indices - finding free "
	   "index...\n", (int)(*colors),(int)num_indices);
#endif

  for (i=0; i<256; i++)
    {
      ix_used[i] = (gboolean)FALSE;
    }

  for (i=0; i<numpixels; i++)
    {
      if (pixels[i*2+1]) ix_used[pixels[i*2]] = (gboolean)TRUE;
    }
  
  for (i=num_indices-1; i>=0; i--)
    {
      if (ix_used[i] == (gboolean)FALSE)
	{
#ifdef GIFDEBUG
	  g_print ("GIF: Found unused colour index %d.\n",(int)i);
#endif
	  return i;
	}
    }

  /* Couldn't find an unused colour index within the number of
     bits per pixel we wanted.  Will have to increment the number
     of colours in the image and assign a transparent pixel there. */
  if ((*colors) < 256)
    {
      (*colors)++;
      g_print ("GIF: 2nd pass - Increasing bounds and using colour index %d.\n"
	       , (int) (*colors)-1);
      return ((*colors)-1);
    }
  
  g_message (_("GIF: Couldn't simply reduce colors further.\nSaving as opaque.\n"));
  return (-1);
}


void
special_flatten_indexed_alpha (guchar *pixels,
			       int *transparent,
			       int *colors,
			       int numpixels)
{
  guint32 i;

  /* Each transparent pixel in the image is mapped to a uniform value for
     encoding, if image already has <=255 colours */
  
  if ((*transparent) == -1) /* tough, no indices left for the trans. index */
    {
      for (i=0; i<numpixels; i++)
	pixels[i] = pixels[i*2];
    }
  else  /* make transparent */
    {
      for (i=0; i<numpixels; i++)
	{
	  if (!(pixels[i*2+1] & 128))
	    {
	      pixels[i] = (guchar)(*transparent);
	    }
	  else
	    {
	      pixels[i] = pixels[i*2];
	    }
	}
    }


  /* Pixel data now takes half as much space (the alpha data has been
     discarded) */
  /*  pixels = g_realloc (pixels, numpixels);*/
}


int
parse_ms_tag (char *str)
{
  gint sum = 0;
  gint offset = 0;
  gint length;

  length = strlen(str);

find_another_bra:

  while ((offset<length) && (str[offset]!='('))
    offset++;
  
  if (offset>=length)
    return(-1);

  if (!isdigit(str[++offset]))
    goto find_another_bra;

  do
    {
      sum *= 10;
      sum += str[offset] - '0';
      offset++;
    }
  while ((offset<length) && (isdigit(str[offset])));  

  if (length-offset <= 2)
    return(-3);

  if ((toupper(str[offset]) != 'M') || (toupper(str[offset+1]) != 'S'))
    return(-4);

  return (sum);
}


int
parse_disposal_tag (char *str)
{
  gint offset = 0;
  gint length;

  length = strlen(str);

  while ((offset+9)<=length)
    {
      if (strncmp(&str[offset],"(combine)",9)==0) 
	return(0x01);
      if (strncmp(&str[offset],"(replace)",9)==0) 
	return(0x02);
      offset++;
    }

  return (gsvals.default_dispose);
}


static gboolean
boundscheck (gint32 image_ID)
{
  GimpDrawable *drawable;
  gint32 *layers;   
  gint nlayers;
  gint i;
  gint offset_x, offset_y;

  /* get a list of layers for this image_ID */
  layers = gimp_image_get_layers (image_ID, &nlayers);  


  /*** Iterate through the layers to make sure they're all ***/
  /*** within the bounds of the image                      ***/

  for (i=0;i<nlayers;i++)
    {
      drawable = gimp_drawable_get (layers[i]);
      gimp_drawable_offsets (layers[i], &offset_x, &offset_y);

      if ((offset_x < 0) ||
	  (offset_y < 0) ||
	  (offset_x+drawable->width > gimp_image_width(image_ID)) ||
	  (offset_y+drawable->height > gimp_image_height(image_ID)))
	{
	  g_free (layers);
	  gimp_drawable_detach(drawable);

	  /* Image has illegal bounds - ask the user what it wants to do */

	  /* Do the crop if we can't talk to the user, or if we asked
	   * the user and they said yes. */
	  if ((run_mode == GIMP_RUN_NONINTERACTIVE) || badbounds_dialog ())
	    {
	      gimp_crop (image_ID,
			 gimp_image_width (image_ID), gimp_image_height (image_ID), 
			 0, 0);
	      return TRUE;
	    }
	  else
	    {
	      return FALSE;
	    }
	}
      else
	gimp_drawable_detach(drawable);
    }

  g_free (layers);

  return TRUE;
}


static gint
save_image (gchar  *filename,
	    gint32  image_ID,
	    gint32  drawable_ID,
	    gint32  orig_image_ID)
{
  GimpPixelRgn pixel_rgn;
  GimpDrawable *drawable;
  GimpImageType drawable_type;
  FILE *outfile;
  int Red[MAXCOLORS];
  int Green[MAXCOLORS];
  int Blue[MAXCOLORS];
  guchar *cmap;
  guint rows, cols;
  int BitsPerPixel, liberalBPP=0, useBPP=0;
  int colors;
  char *temp_buf;
  int i;
  int transparent;
  gint offset_x, offset_y;

  gint32 *layers;   
  int nlayers;

  gboolean is_gif89 = FALSE;

  int Delay89;
  int Disposal;
  char *layer_name;

  unsigned char bgred, bggreen, bgblue;


#ifdef FACEHUGGERS
  /* Save the comment back to the ImageID, if appropriate */
  if (globalcomment != NULL && comment_was_edited)
    {
      comment_parasite = gimp_parasite_new ("gimp-comment",
					    GIMP_PARASITE_PERSISTENT,
					    strlen (globalcomment)+1,
					    (void*) globalcomment);
      gimp_image_parasite_attach (orig_image_ID, comment_parasite);
      gimp_parasite_free (comment_parasite);
      comment_parasite = NULL;
    }
#endif


  /* get a list of layers for this image_ID */
  layers = gimp_image_get_layers (image_ID, &nlayers);  


  drawable_type = gimp_drawable_type (layers[0]);


  /* If the image has multiple layers (i.e. will be animated), a comment,
     or transparency, then it must be encoded as a GIF89a file, not a vanilla
     GIF87a. */
  if (nlayers > 1)
    is_gif89 = TRUE;

  if (gsvals.save_comment)
    is_gif89 = TRUE;

  switch (drawable_type)
    {
    case GIMP_INDEXEDA_IMAGE:
      is_gif89 = TRUE;
    case GIMP_INDEXED_IMAGE:
      cmap = gimp_image_get_cmap (image_ID, &colors);
      
      gimp_palette_get_background(&bgred, &bggreen, &bgblue);

      for (i = 0; i < colors; i++)
	{
	  Red[i] = *cmap++;
	  Green[i] = *cmap++;
	  Blue[i] = *cmap++;
	}
      for ( ; i < 256; i++)
	{
	  Red[i] = bgred;
	  Green[i] = bggreen;
	  Blue[i] = bgblue;
	}
      break;
    case GIMP_GRAYA_IMAGE:
      is_gif89 = TRUE;
    case GIMP_GRAY_IMAGE:
      colors = 256;                   /* FIXME: Not ideal. */
      for ( i = 0;  i < 256; i++)
	{
	  Red[i] = Green[i] = Blue[i] = i;
	}
      break;

    default:
      g_message (_("GIF: Sorry, can't save RGB images as GIFs - convert to INDEXED\nor GRAY first.\n"));
      return FALSE;
      break;
    }

  if (run_mode != GIMP_RUN_NONINTERACTIVE)
    {
      /* init the progress meter */    
      temp_buf = g_strdup_printf (_("Saving %s:"), filename);
      gimp_progress_init (temp_buf);
      g_free (temp_buf);
    }
  

  /* open the destination file for writing */
  outfile = fopen (filename, "wb");
  if (!outfile)
    {
      g_message (_("GIF: can't open %s\n"), filename);
      return FALSE;
    }


  /* write the GIFheader */

  if (colors < 256)
    {
      /* we keep track of how many bits we promised to have in liberalBPP,
	 so that we don't accidentally come under this when doing
	 clever transparency stuff where we can re-use wasted indices. */
      liberalBPP = BitsPerPixel =
	colorstobpp (colors + ((drawable_type==GIMP_INDEXEDA_IMAGE) ? 1 : 0));
    }
  else
    {
      liberalBPP = BitsPerPixel =
	colorstobpp (256);

      if (drawable_type==GIMP_INDEXEDA_IMAGE)
	{
	  g_print ("GIF: Too many colours?\n");
	}
    }

  cols = gimp_image_width (image_ID);
  rows = gimp_image_height (image_ID);
  Interlace = gsvals.interlace;
  GIFEncodeHeader (outfile, is_gif89, cols, rows, 0,
		   BitsPerPixel, Red, Green, Blue, GetPixel);


  /* If the image has multiple layers it'll be made into an
     animated GIF, so write out the infinite-looping extension */
  if ((nlayers > 1) && (gsvals.loop))
    GIFEncodeLoopExt (outfile, 0);

  /* Write comment extension - mustn't be written before the looping ext. */
  if (gsvals.save_comment)
    {
      GIFEncodeCommentExt (outfile, globalcomment);
    }



  /*** Now for each layer in the image, save an image in a compound GIF ***/
  /************************************************************************/

  i = nlayers-1;

  while (i >= 0)
    {
      drawable_type = gimp_drawable_type (layers[i]);
      drawable = gimp_drawable_get (layers[i]);
      gimp_drawable_offsets (layers[i], &offset_x, &offset_y);
      cols = drawable->width;
      rows = drawable->height;
      rowstride = drawable->width;
      
      gimp_pixel_rgn_init (&pixel_rgn, drawable, 0, 0,
			   drawable->width, drawable->height, FALSE, FALSE);

      cur_progress = 0;
      max_progress = drawable->height;
      
      pixels = (guchar *) g_malloc (drawable->width *
				    drawable->height *
				    (((drawable_type == GIMP_INDEXEDA_IMAGE)||
				      (drawable_type == GIMP_GRAYA_IMAGE)) ? 2:1) );
      
      gimp_pixel_rgn_get_rect (&pixel_rgn, pixels, 0, 0,
			       drawable->width, drawable->height);


      /* sort out whether we need to do transparency jiggery-pokery */
      if ((drawable_type == GIMP_INDEXEDA_IMAGE)||(drawable_type == GIMP_GRAYA_IMAGE))
	{
	  /* Try to find an entry which isn't actually used in the
	     image, for a transparency index. */
	  
	  transparent =
	    find_unused_ia_colour(pixels,
				  drawable->width * drawable->height,
				  bpptocolors(colorstobpp(colors)),
				  &colors);

	  special_flatten_indexed_alpha (pixels,
					 &transparent,
					 &colors,
					 drawable->width * drawable->height);
	}
      else
	transparent = -1;
      
      
      BitsPerPixel = colorstobpp (colors);

      if (BitsPerPixel != liberalBPP)
	{
	  /* We were able to re-use an index within the existing bitspace,
	     whereas the estimate in the header was pessimistic but still
	     needs to be upheld... */
#ifdef GIFDEBUG
	  g_warning("Promised %d bpp, pondered writing chunk with %d bpp!",
		    liberalBPP, BitsPerPixel);
#endif
	  g_warning ("Transparent colour *might* be incorrect "
		      "on viewers which don't support transparency.");
	}
      useBPP = (BitsPerPixel > liberalBPP) ? BitsPerPixel : liberalBPP;

      
      if (is_gif89)
	{
	  if (i>0)
	    {
	      layer_name = gimp_layer_get_name(layers[i-1]);
	      Disposal = parse_disposal_tag(layer_name);
	      g_free(layer_name);
	    }
	  else
	    Disposal = gsvals.default_dispose;

	  layer_name = gimp_layer_get_name(layers[i]);
	  Delay89 = parse_ms_tag(layer_name);
	  g_free(layer_name);

	  if (Delay89 < 0)
	    Delay89 = (gsvals.default_delay + 5) / 10;
	  else
	    Delay89 = (Delay89 + 5) / 10;

	  /* don't allow a CPU-sucking completely 0-delay looping anim */
	  if ((nlayers > 1) &&
	      gsvals.loop &&
	      (Delay89 == 0))
	    {
	      static gboolean onceonly = FALSE;

	      if (!onceonly)
		{
		  g_warning("GIF plugin: Delay inserted to prevent evil "
			    "CPU-sucking anim.\n");
		  onceonly = TRUE;
		}
	      Delay89 = 1;
	    }

	  GIFEncodeGraphicControlExt (outfile, Disposal, Delay89, nlayers,
				      cols, rows, 0,
				      transparent,
				      useBPP,
				      Red, Green,
				      Blue, GetPixel);
	}

      GIFEncodeImageData (outfile, cols, rows,
			  (rows>4) ? gsvals.interlace : 0,
			  0, transparent,
			  useBPP,
			  Red, Green, Blue, GetPixel,
			  offset_x, offset_y);

      
      
      gimp_drawable_detach (drawable);
      
      g_free (pixels);

      i--;
    }
  
  g_free(layers);

  GIFEncodeClose (outfile, cols, rows, gsvals.interlace, 0, transparent,
		  useBPP, Red, Green, Blue, GetPixel);

  return TRUE;
}

static gboolean
badbounds_dialog (void)
{
  GtkWidget *dlg;
  GtkWidget *label;
  GtkWidget *frame;
  GtkWidget *vbox;

  dlg = gimp_dialog_new (_("GIF Warning"), "gif_warning",
			 gimp_standard_help_func, "filters/gif.html#warning",
			 GTK_WIN_POS_MOUSE,
			 FALSE, FALSE, FALSE,

			 _("OK"), cropok_callback,
			 NULL, NULL, NULL, TRUE, FALSE,
			 _("Cancel"), gtk_widget_destroy,
			 NULL, 1, NULL, FALSE, TRUE,

			 NULL);

  gtk_signal_connect (GTK_OBJECT (dlg), "destroy",
		      GTK_SIGNAL_FUNC (gtk_main_quit),
		      NULL);

  /*  the warning message  */
  frame = gtk_frame_new (NULL);
  gtk_frame_set_shadow_type (GTK_FRAME (frame), GTK_SHADOW_ETCHED_IN);
  gtk_container_set_border_width (GTK_CONTAINER (frame), 6);
  gtk_box_pack_start (GTK_BOX (GTK_DIALOG (dlg)->vbox), frame, TRUE, TRUE, 0);

  vbox = gtk_vbox_new (FALSE, 4);
  gtk_container_set_border_width (GTK_CONTAINER (vbox), 4);
  gtk_container_add (GTK_CONTAINER (frame), vbox);
  
  label= gtk_label_new (_("The image which you are trying to save as a GIF\n"
			  "contains layers which extend beyond the actual\n"
			  "borders of the image.  This isn't allowed in GIFs,\n"
			  "I'm afraid.\n\n"
			  "You may choose whether to crop all of the layers to\n"
			  "the image borders, or cancel this save."));
  gtk_box_pack_start (GTK_BOX (vbox), label, TRUE, TRUE, 0);
  gtk_widget_show (label);

  gtk_widget_show (vbox);
  gtk_widget_show (frame);

  gtk_widget_show (dlg);

  gtk_main ();
  gdk_flush ();

  return can_crop;
}


static gint
save_dialog (gint32 image_ID)
{
  GtkWidget *dlg;
  GtkWidget *main_vbox;
  GtkWidget *toggle;
  GtkWidget *label;
  GtkWidget *spinbutton;
  GtkObject *adj;
  GtkWidget *text;
  GtkWidget *frame;
  GtkWidget *vbox;
  GtkWidget *hbox;
  GtkWidget *disposal_option_menu;
  GtkWidget *com_table;
  GtkWidget *vscrollbar;
#ifdef FACEHUGGERS
  GimpParasite* GIF2_CMNT;
#endif

  gint32 nlayers;

  gimp_image_get_layers (image_ID, &nlayers);

  dlg = gimp_dialog_new (_("Save as GIF"), "gif",
			 gimp_standard_help_func, "filters/gif.html",
			 GTK_WIN_POS_MOUSE,
			 FALSE, TRUE, FALSE,

			 _("OK"), save_ok_callback,
			 NULL, NULL, NULL, TRUE, FALSE,
			 _("Cancel"), gtk_widget_destroy,
			 NULL, 1, NULL, FALSE, TRUE,

			 NULL);

  gtk_signal_connect (GTK_OBJECT (dlg), "destroy",
		      GTK_SIGNAL_FUNC (gtk_main_quit),
		      NULL);

  main_vbox = gtk_vbox_new (FALSE, 4);
  gtk_container_set_border_width (GTK_CONTAINER (main_vbox), 6);
  gtk_container_add (GTK_CONTAINER (GTK_DIALOG (dlg)->vbox), main_vbox);
  gtk_widget_show (main_vbox);

  /*  regular gif parameter settings  */
  frame = gtk_frame_new (_("GIF Options"));
  gtk_frame_set_shadow_type (GTK_FRAME (frame), GTK_SHADOW_ETCHED_IN);
  gtk_box_pack_start (GTK_BOX (main_vbox), frame, TRUE, TRUE, 0);

  vbox = gtk_vbox_new (FALSE, 4);
  gtk_container_set_border_width (GTK_CONTAINER (vbox), 4);
  gtk_container_add (GTK_CONTAINER (frame), vbox);

  toggle = gtk_check_button_new_with_label (_("Interlace"));
  gtk_box_pack_start (GTK_BOX (vbox), toggle, FALSE, FALSE, 0);
  gtk_signal_connect (GTK_OBJECT (toggle), "toggled",
		      GTK_SIGNAL_FUNC (gimp_toggle_button_update),
		      &gsvals.interlace);
  gtk_toggle_button_set_active (GTK_TOGGLE_BUTTON (toggle), gsvals.interlace);
  gtk_widget_show (toggle);

  hbox = gtk_hbox_new (FALSE, 4);
  gtk_box_pack_start (GTK_BOX (vbox), hbox, TRUE, TRUE, 0);

  toggle = gtk_check_button_new_with_label (_("GIF Comment:"));
  gtk_box_pack_start (GTK_BOX (hbox), toggle, FALSE, FALSE, 0);
  gtk_signal_connect (GTK_OBJECT (toggle), "toggled",
		      GTK_SIGNAL_FUNC (gimp_toggle_button_update),
		      &gsvals.save_comment);
  gtk_toggle_button_set_active (GTK_TOGGLE_BUTTON (toggle), gsvals.save_comment);
  gtk_widget_show (toggle);

  com_table = gtk_table_new (1, 1, FALSE);
  gtk_box_pack_start (GTK_BOX (hbox), com_table, TRUE, TRUE, 0);

  text = gtk_text_new (NULL, NULL);
  gtk_text_set_editable (GTK_TEXT (text), TRUE);
  gtk_widget_set_usize (text, 80,3);
  gtk_table_attach (GTK_TABLE (com_table), text, 0, 1, 0, 1,
                    GTK_EXPAND | GTK_SHRINK | GTK_FILL,
                    GTK_EXPAND | GTK_SHRINK | GTK_FILL, 0, 0);
  
  if (globalcomment != NULL)
    {
      g_free (globalcomment);
    }
#ifdef FACEHUGGERS
  GIF2_CMNT = gimp_image_parasite_find (image_ID, "gimp-comment");
  if (GIF2_CMNT)
    {
      globalcomment = g_malloc (GIF2_CMNT->size+1);
      memcpy (globalcomment, GIF2_CMNT->data, GIF2_CMNT->size);
      globalcomment[GIF2_CMNT->size] = 0;
    }
  else
    {
#endif
      /*	globalcomment = g_malloc(1+strlen(_("Made with GIMP")));
		strcpy(globalcomment, _("Made with GIMP")); */
      globalcomment = NULL;
#ifdef FACEHUGGERS
    }
  gimp_parasite_free (GIF2_CMNT);
#endif

  if (globalcomment)
    gtk_text_insert (GTK_TEXT (text), NULL, NULL, NULL, globalcomment, -1);
  gtk_signal_connect (GTK_OBJECT (text), "changed",
		      GTK_SIGNAL_FUNC (comment_entry_callback),
		      NULL);

  vscrollbar = gtk_vscrollbar_new (GTK_TEXT (text)->vadj);
  gtk_table_attach (GTK_TABLE (com_table), vscrollbar, 1, 2, 0, 1,
		    GTK_FILL, GTK_EXPAND | GTK_SHRINK | GTK_FILL, 0, 0);
  gtk_widget_show (vscrollbar);
  gtk_widget_show (text);
  gtk_widget_show (com_table);

  gtk_widget_show (hbox);

  gtk_widget_show (vbox);
  gtk_widget_show (frame);

  /*  additional animated gif parameter settings  */
  frame = gtk_frame_new (_("Animated GIF Options"));
  gtk_frame_set_shadow_type (GTK_FRAME (frame), GTK_SHADOW_ETCHED_IN);
  gtk_box_pack_start (GTK_BOX (main_vbox), frame, FALSE, FALSE, 0);

  vbox = gtk_vbox_new (FALSE, 4);
  gtk_container_set_border_width (GTK_CONTAINER (vbox), 4);
  gtk_container_add (GTK_CONTAINER (frame), vbox);

  toggle = gtk_check_button_new_with_label (_("Loop forever"));
  gtk_box_pack_start (GTK_BOX (vbox), toggle, FALSE, FALSE, 0);
  gtk_signal_connect (GTK_OBJECT (toggle), "toggled",
		      GTK_SIGNAL_FUNC (gimp_toggle_button_update),
		      &gsvals.loop);
  gtk_toggle_button_set_active (GTK_TOGGLE_BUTTON (toggle), gsvals.loop);
  gtk_widget_show (toggle);

  /* default_delay entry field */
  hbox = gtk_hbox_new (FALSE, 4);
  gtk_box_pack_start (GTK_BOX (vbox), hbox, FALSE, FALSE, 0);

  label = gtk_label_new (_("Delay between Frames where Unspecified:"));
  gtk_box_pack_start (GTK_BOX (hbox), label, FALSE, FALSE, 0);
  gtk_widget_show (label);

  spinbutton = gimp_spin_button_new (&adj, gsvals.default_delay,
				     0, 65000, 10, 100, 0, 1, 0);
  gtk_box_pack_start (GTK_BOX (hbox), spinbutton, FALSE, FALSE, 0);
  gtk_signal_connect (GTK_OBJECT (adj), "value_changed",
                      GTK_SIGNAL_FUNC (gimp_int_adjustment_update),
                      &gsvals.default_delay);
  gtk_widget_show (spinbutton);

  label = gtk_label_new (_("Milliseconds"));
  gtk_box_pack_start (GTK_BOX (hbox), label, FALSE, FALSE, 0);
  gtk_widget_show (label);

  gtk_widget_show (hbox);

  /* Disposal selector */
  hbox = gtk_hbox_new (FALSE, 4);
  gtk_box_pack_start (GTK_BOX (vbox), hbox, FALSE, FALSE, 0);

  label = gtk_label_new (_("Frame Disposal where Unspecified: "));
  gtk_box_pack_start (GTK_BOX (hbox), label, FALSE, FALSE, 0);
  gtk_widget_show (label);

  disposal_option_menu =
    gimp_option_menu_new2 (FALSE, gimp_menu_item_update,
			   &gsvals.default_dispose,
			   (gpointer) gsvals.default_dispose,

			   _("I don't Care"),
			   (gpointer) DISPOSE_UNSPECIFIED, NULL,
			   _("Cumulative Layers (Combine)"),
			   (gpointer) DISPOSE_COMBINE, NULL,
			   _("One Frame per Layer (Replace)"),
			   (gpointer) DISPOSE_REPLACE, NULL,

			   NULL);
  gtk_box_pack_start (GTK_BOX (hbox), disposal_option_menu, FALSE, FALSE, 0);
  gtk_widget_show (disposal_option_menu);

  gtk_widget_show (hbox);
  gtk_widget_show (vbox);

  /* If the image has only one layer it can't be animated, so
     desensitize the animation options. */

  if (nlayers == 1) gtk_widget_set_sensitive (frame, FALSE);

  gtk_widget_show (frame);

  gtk_widget_show (dlg);

  gtk_main ();
  gdk_flush ();

  return gsint.run;
}


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 if (colors <= 256)
    bpp = 8;
  else
    {
      g_warning ("GIF: colorstobpp - Eep! too many colours: %d\n", colors);
      return 8;
    }

  return bpp;
}



static int
bpptocolors (int bpp)
{
  int colors;

  if (bpp>8)
    {
      g_warning ("GIF: bpptocolors - Eep! bpp==%d !\n", bpp);
      return 256;
    }
  
  colors = 1 << bpp;

  return (colors);
}



static int
GetPixel (int x,
	  int y)
{
  return *(pixels + (rowstride * (long) y) + (long) x);
}


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

static gint  Width, Height;
static gint  curx, cury;
static glong CountDown;
static gint  Pass = 0;

/*
 * Bump the 'curx' and 'cury' to point to the next pixel
 */
static void
BumpPixel (void)
{
  /*
   * 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)
    {
      if (run_mode != GIMP_RUN_NONINTERACTIVE)
	{
	  cur_progress++;
	  if ((cur_progress % 16) == 0)
	    gimp_progress_update ((double) cur_progress / (double) max_progress);
	}

      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;
}

/* public */

static void
GIFEncodeHeader (FILE    *fp,
		 gboolean gif89,
		 int      GWidth,
		 int      GHeight,
		 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;

  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 (gif89 ? "GIF89a" : "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);
    }
}


static void
GIFEncodeGraphicControlExt (FILE    *fp,
			    int      Disposal,
			    int      Delay89,
			    int      NumFramesInImage,
			    int      GWidth,
			    int      GHeight,
			    int      Background,
			    int      Transparent,
			    int      BitsPerPixel,
			    int      Red[],
			    int      Green[],
			    int      Blue[],
			    ifunptr  GetPixel)
{
  int RWidth, RHeight;
  int LeftOfs, TopOfs;
  int Resolution;
  int ColorMapSize;
  int InitCodeSize;

  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 out extension for transparent colour index, if necessary.
   */
  if ( (Transparent >= 0) || (NumFramesInImage > 1) )
    {
      /* Extension Introducer - fixed. */
      fputc ('!', fp);
      /* Graphic Control Label - fixed. */
      fputc (0xf9, fp);
      /* Block Size - fixed. */
      fputc (4, fp);
      
      /* Packed Fields - XXXdddut (d=disposal, u=userInput, t=transFlag) */
      /*                    s8421                                        */
      fputc ( ((Transparent >= 0) ? 0x01 : 0x00) /* TRANSPARENCY */

	      /* DISPOSAL */
	      | ((NumFramesInImage > 1) ? (Disposal << 2) : 0x00 ),
	      /* 0x03 or 0x01 build frames cumulatively */
	      /* 0x02 clears frame before drawing */
	      /* 0x00 'don't care' */

	      fp);
      
      fputc (Delay89 & 255, fp);
      fputc ((Delay89>>8) & 255, fp);

      fputc (Transparent, fp);
      fputc (0, fp);
    }
}


static void
GIFEncodeImageData (FILE    *fp,
		    int      GWidth,
		    int      GHeight,
		    int      GInterlace,
		    int      Background,
		    int      Transparent,
		    int      BitsPerPixel,
		    int      Red[],
		    int      Green[],
		    int      Blue[],
		    ifunptr  GetPixel,
		    gint     offset_x,
		    gint     offset_y)
{
  int RWidth, RHeight;
  int LeftOfs, TopOfs;
  int Resolution;
  int ColorMapSize;
  int InitCodeSize;

  Interlace = GInterlace;

  ColorMapSize = 1 << BitsPerPixel;

  RWidth = Width = GWidth;
  RHeight = Height = GHeight;
  LeftOfs = (int) offset_x;
  TopOfs = (int) offset_y;

  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;

#if 0
  /*
   * 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);


  /***************************/
  Interlace = GInterlace;
  ColorMapSize = 1 << BitsPerPixel;
  RWidth = Width = GWidth;
  RHeight = Height = GHeight;
  LeftOfs = TopOfs = 0;
  Resolution = BitsPerPixel;

  CountDown = (long) Width *(long) Height;
  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;

#endif


  cur_progress = 0;


  /*
   * 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);
}


static void
GIFEncodeClose (FILE    *fp,
		int      GWidth,
		int      GHeight,
		int      GInterlace,
		int      Background,
		int      Transparent,
		int      BitsPerPixel,
		int      Red[],
		int      Green[],
		int      Blue[],
		ifunptr  GetPixel)
{
  /*
   * Write the GIF file terminator
   */
  fputc (';', fp);

  /*
   * And close the file
   */
  fclose (fp);
}


static void
GIFEncodeLoopExt (FILE    *fp,
		  guint    num_loops)
{
  fputc(0x21,fp);
  fputc(0xff,fp);
  fputc(0x0b,fp);
  fputs("NETSCAPE2.0",fp);
  fputc(0x03,fp);
  fputc(0x01,fp);
  Putword(num_loops,fp);
  fputc(0x00,fp);

  /* NOTE: num_loops==0 means 'loop infinitely' */
}


static void GIFEncodeCommentExt (FILE *fp, char *comment)
{
  if (!comment || !*comment)
    return;

  if (strlen(comment)>240)
    {
      g_print ("GIF: warning: comment too large - comment block not written.\n");
      return;
    }

  fputc(0x21,fp);
  fputc(0xfe,fp);
  fputc(strlen(comment),fp);
  fputs((const char *)comment,fp);
  fputc(0x00,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 GIF_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 = GIF_BITS;	/* user settable max # bits/code */
static code_int maxcode;	/* maximum code, given n_bits */
static code_int maxmaxcode = (code_int) 1 << GIF_BITS;	/* should NEVER generate this code */
#ifdef COMPATIBLE		/* But wrong! */
#define MAXCODE(Mn_bits)        ((code_int) 1 << (Mn_bits) - 1)
#else /*COMPATIBLE */
#define MAXCODE(Mn_bits)        (((code_int) 1 << (Mn_bits)) - 1)
#endif /*COMPATIBLE */

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

const code_int hsize = HSIZE;	/* the original reason for this being
				   variable was "for dynamic table sizing",
				   but since it was never actually changed
				   I made it const   --Adam. */

/*
 * 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**GIF_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<<GIF_BITS))

static code_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 int offset;
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 unsigned long cur_accum;
static int cur_bits;

static unsigned long masks[] =
{0x0000, 0x0001, 0x0003, 0x0007, 0x000F,
 0x001F, 0x003F, 0x007F, 0x00FF,
 0x01FF, 0x03FF, 0x07FF, 0x0FFF,
 0x1FFF, 0x3FFF, 0x7FFF, 0xFFFF};


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;

  cur_bits = 0;
  cur_accum = 0;

  /*
   * Set up the necessary values
   */
  offset = 0;
  out_count = 0;
  clear_flg = 0;
  in_count = 1;

  ClearCode = (1 << (init_bits - 1));
  EOFCode = ClearCode + 1;
  free_ent = ClearCode + 2;


  /* Had some problems here... should be okay now.  --Adam */
  n_bits = g_init_bits;
  maxcode = MAXCODE (n_bits);



  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 GIF_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);

      if (ferror (g_outfile))
	writeerr ();
    }
}

/*
 * 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;
}

static void
writeerr ()
{
  g_message (_("GIF: error writing output file\n"));
  return;
}

/******************************************************************************
 *
 * 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 (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;
    }
}


/* crop dialog functions */

static void
cropok_callback (GtkWidget *widget,
		 gpointer   data)
{
  can_crop = TRUE;

  gtk_widget_destroy (GTK_WIDGET (data));
}

/*  Save interface functions  */

static void
save_ok_callback (GtkWidget *widget,
		  gpointer   data)
{
  gsint.run = TRUE;

  gtk_widget_destroy (GTK_WIDGET (data));
}

static void
comment_entry_callback (GtkWidget *widget,
			gpointer   data)
{
  gint ssize;
  gchar* str;

  str = gtk_editable_get_chars (GTK_EDITABLE (widget), 0, -1);
  ssize = strlen (str);

  /* Temporary kludge for overlength strings - just return */
  if (ssize > 240)
    {
      g_message (_("GIF save: Your comment string is too long.\n"));
      g_free (str);
      return;
    }

  if (globalcomment != NULL) g_free (globalcomment);
  globalcomment = g_malloc (ssize + 1);

  /*strcpy(globalcomment, gtk_entry_get_text (GTK_ENTRY (widget)));*/
  strcpy (globalcomment, str);
  g_free (str);

  comment_was_edited = TRUE;

  /*g_print ("COMMENT: %s\n",globalcomment);*/
}