/*
 * Animation Optimizer plug-in version 1.1.2
 *
 * (c) Adam D. Moss, 1997-2003
 *     adam@gimp.org
 *     adam@foxbox.org
 *
 * GIMP - The GNU Image Manipulation Program
 * Copyright (C) 1995 Spencer Kimball and Peter Mattis
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

/*
#define EXPERIMENTAL_BACKDROP_CODE
*/


#include "config.h"

#include <string.h>

#include <libgimp/gimp.h>

#include "libgimp/stdplugins-intl.h"


#define OPTIMIZE_PROC        "plug-in-animationoptimize"
#define OPTIMIZE_DIFF_PROC   "plug-in-animationoptimize-diff"
#define UNOPTIMIZE_PROC      "plug-in-animationunoptimize"
#define REMOVE_BACKDROP_PROC "plug-in-animation-remove-backdrop"
#define FIND_BACKDROP_PROC   "plug-in-animation-find-backdrop"


typedef enum
{
  DISPOSE_UNDEFINED = 0x00,
  DISPOSE_COMBINE   = 0x01,
  DISPOSE_REPLACE   = 0x02
} DisposeType;


typedef enum
{
  OPOPTIMIZE   = 0L,
  OPUNOPTIMIZE = 1L,
  OPFOREGROUND = 2L,
  OPBACKGROUND = 3L
} operatingMode;


/* Declare local functions. */
static  void query (void);
static  void run   (const gchar      *name,
                    gint              nparams,
                    const GimpParam  *param,
                    gint             *nreturn_vals,
                    GimpParam       **return_vals);

static  gint32      do_optimizations    (GimpRunMode  run_mode,
                                         gboolean     diff_only);

/* tag util functions*/
static  gint        parse_ms_tag        (const gchar *str);
static  DisposeType parse_disposal_tag  (const gchar *str);
static  DisposeType get_frame_disposal  (guint        whichframe);
static  guint32     get_frame_duration  (guint        whichframe);
static  void        remove_disposal_tag (gchar       *dest,
                                         gchar       *src);
static  void        remove_ms_tag       (gchar       *dest,
                                         gchar       *src);
static  gboolean    is_disposal_tag     (const gchar *str,
                                         DisposeType *disposal,
                                         gint        *taglength);
static  gboolean    is_ms_tag           (const gchar *str,
                                         gint        *duration,
                                         gint        *taglength);


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


/* Global widgets'n'stuff */
static  guint             width, height;
static  gint32            image_id;
static  gint32            new_image_id;
static  gint32            total_frames;
static  gint32           *layers;
static  GimpImageBaseType imagetype;
static  GimpImageType     drawabletype_alpha;
static  guchar            pixelstep;
static  guchar           *palette;
static  gint              ncolors;
static  operatingMode     opmode;


MAIN ()

static void
query (void)
{
  static const GimpParamDef args[] =
  {
    { GIMP_PDB_INT32,    "run-mode", "The run mode { RUN-INTERACTIVE (0), RUN-NONINTERACTIVE (1) }" },
    { GIMP_PDB_IMAGE,    "image",    "Input image"                  },
    { GIMP_PDB_DRAWABLE, "drawable", "Input drawable (unused)"      }
  };
  static const GimpParamDef return_args[] =
  {
    { GIMP_PDB_IMAGE, "result", "Resulting image" }
  };

  gimp_install_procedure (OPTIMIZE_PROC,
                          N_("Modify image to reduce size when saved as GIF animation"),
                          "This procedure applies various optimizations to"
                          " a GIMP layer-based animation in an attempt to"
                          " reduce the final file size.  If a frame of the"
                          " animation can use the 'combine' mode, this"
                          " procedure attempts to maximize the number of"
                          " ajdacent pixels having the same color, which"
                          " improves the compression for some image formats"
                          " such as GIF or MNG.",
                          "Adam D. Moss <adam@gimp.org>",
                          "Adam D. Moss <adam@gimp.org>",
                          "1997-2003",
                          N_("Optimize (for _GIF)"),
                          "RGB*, INDEXED*, GRAY*",
                          GIMP_PLUGIN,
                          G_N_ELEMENTS (args),
                          G_N_ELEMENTS (return_args),
                          args, return_args);

  gimp_install_procedure (OPTIMIZE_DIFF_PROC,
                          N_("Reduce file size where combining layers is possible"),
                          "This procedure applies various optimizations to"
                          " a GIMP layer-based animation in an attempt to"
                          " reduce the final file size.  If a frame of the"
                          " animation can use the 'combine' mode, this"
                          " procedure uses a simple difference between the"
                          " frames.",
                          "Adam D. Moss <adam@gimp.org>",
                          "Adam D. Moss <adam@gimp.org>",
                          "1997-2001",
                          N_("_Optimize (Difference)"),
                          "RGB*, INDEXED*, GRAY*",
                          GIMP_PLUGIN,
                          G_N_ELEMENTS (args),
                          G_N_ELEMENTS (return_args),
                          args, return_args);

  gimp_install_procedure (UNOPTIMIZE_PROC,
                          N_("Remove optimization to make editing easier"),
                          "This procedure 'simplifies' a GIMP layer-based"
                          " animation that has been optimized for animation. "
                          "This makes editing the animation much easier.",
                          "Adam D. Moss <adam@gimp.org>",
                          "Adam D. Moss <adam@gimp.org>",
                          "1997-2001",
                          N_("_Unoptimize"),
                          "RGB*, INDEXED*, GRAY*",
                          GIMP_PLUGIN,
                          G_N_ELEMENTS (args),
                          G_N_ELEMENTS (return_args),
                          args, return_args);

  gimp_plugin_menu_register (OPTIMIZE_PROC,      "<Image>/Filters/Animation");
  gimp_plugin_menu_register (OPTIMIZE_DIFF_PROC, "<Image>/Filters/Animation");
  gimp_plugin_menu_register (UNOPTIMIZE_PROC,    "<Image>/Filters/Animation");

#ifdef EXPERIMENTAL_BACKDROP_CODE
  gimp_install_procedure (REMOVE_BACKDROP_PROC,
                          "This procedure attempts to remove the backdrop"
                          " from a GIMP layer-based animation, leaving"
                          " the foreground animation over transparency.",
                          "",
                          "Adam D. Moss <adam@gimp.org>",
                          "Adam D. Moss <adam@gimp.org>",
                          "2001",
                          N_("_Remove Backdrop"),
                          "RGB*, INDEXED*, GRAY*",
                          GIMP_PLUGIN,
                          G_N_ELEMENTS (args),
                          G_N_ELEMENTS (return_args),
                          args, return_args);

  gimp_install_procedure (FIND_BACKDROP_PROC,
                          "This procedure attempts to remove the foreground"
                          " from a GIMP layer-based animation, leaving"
                          " a one-layered image containing only the"
                          " constant backdrop image.",
                          "",
                          "Adam D. Moss <adam@gimp.org>",
                          "Adam D. Moss <adam@gimp.org>",
                          "2001",
                          N_("_Find Backdrop"),
                          "RGB*, INDEXED*, GRAY*",
                          GIMP_PLUGIN,
                          G_N_ELEMENTS (args),
                          G_N_ELEMENTS (return_args),
                          args, return_args);

  gimp_plugin_menu_register (REMOVE_BACKDROP_PROC, "<Image>/Filters/Animation");
  gimp_plugin_menu_register (FIND_BACKDROP_PROC,   "<Image>/Filters/Animation");
#endif
}

static void
run (const gchar      *name,
     gint              n_params,
     const GimpParam  *param,
     gint             *nreturn_vals,
     GimpParam       **return_vals)
{
  static GimpParam  values[2];
  GimpRunMode       run_mode;
  GimpPDBStatusType status    = GIMP_PDB_SUCCESS;
  gboolean          diff_only = FALSE;

  *nreturn_vals = 2;
  *return_vals  = values;

  run_mode = param[0].data.d_int32;

  INIT_I18N ();
  gegl_init (NULL, NULL);

  if (run_mode == GIMP_RUN_NONINTERACTIVE && n_params != 3)
    {
      status = GIMP_PDB_CALLING_ERROR;
    }

  /* Check the procedure name we were called with, to decide
     what needs to be done. */
  if (strcmp (name, OPTIMIZE_PROC) == 0)
    opmode = OPOPTIMIZE;
  else if (strcmp (name, OPTIMIZE_DIFF_PROC) == 0)
    {
      opmode = OPOPTIMIZE;
      diff_only = TRUE;
    }
  else if (strcmp (name, UNOPTIMIZE_PROC) == 0)
    opmode = OPUNOPTIMIZE;
  else if (strcmp (name, FIND_BACKDROP_PROC) == 0)
    opmode = OPBACKGROUND;
  else if (strcmp (name, REMOVE_BACKDROP_PROC) == 0)
    opmode = OPFOREGROUND;
  else
    g_error("GAH!!!");

  if (status == GIMP_PDB_SUCCESS)
    {
      image_id = param[1].data.d_image;

      new_image_id = do_optimizations (run_mode, diff_only);

      if (run_mode != GIMP_RUN_NONINTERACTIVE)
        gimp_displays_flush();
    }

  values[0].type          = GIMP_PDB_STATUS;
  values[0].data.d_status = status;

  values[1].type         = GIMP_PDB_IMAGE;
  values[1].data.d_image = new_image_id;
}



/* Rendering Functions */

static void
total_alpha (guchar  *imdata,
             guint32  numpix,
             guchar   bytespp)
{
  /* Set image to total-transparency w/black
   */

  memset (imdata, 0, numpix * bytespp);
}

static const Babl *
get_format (gint32 drawable_ID)
{
  if (gimp_drawable_is_rgb (drawable_ID))
    {
      if (gimp_drawable_has_alpha (drawable_ID))
        return babl_format ("R'G'B'A u8");
      else
        return babl_format ("R'G'B' u8");
    }
  else if (gimp_drawable_is_gray (drawable_ID))
    {
      if (gimp_drawable_has_alpha (drawable_ID))
        return babl_format ("Y'A u8");
      else
        return babl_format ("Y' u8");
    }

  return gimp_drawable_get_format (drawable_ID);
}

static void
compose_row (gint          frame_num,
             DisposeType   dispose,
             gint          row_num,
             guchar       *dest,
             gint          dest_width,
             gint32        drawable_ID,
             gboolean      cleanup)
{
  static guchar *line_buf = NULL;
  GeglBuffer    *src_buffer;
  const Babl    *format;
  guchar        *srcptr;
  gint           rawx, rawy, rawbpp, rawwidth, rawheight;
  gint           i;
  gboolean       has_alpha;

  if (cleanup)
    {
      if (line_buf)
        {
          g_free (line_buf);
          line_buf = NULL;
        }

      return;
    }

  if (dispose == DISPOSE_REPLACE)
    {
      total_alpha (dest, dest_width, pixelstep);
    }

  gimp_drawable_offsets (drawable_ID, &rawx, &rawy);

  rawwidth  = gimp_drawable_width (drawable_ID);
  rawheight = gimp_drawable_height (drawable_ID);

  /* this frame has nothing to give us for this row; return */
  if (row_num >= rawheight + rawy ||
      row_num < rawy)
    return;

  format = get_format (drawable_ID);

  has_alpha = gimp_drawable_has_alpha (drawable_ID);
  rawbpp    = babl_format_get_bytes_per_pixel (format);

  if (line_buf)
    {
      g_free (line_buf);
      line_buf = NULL;
    }
  line_buf = g_malloc (rawwidth * rawbpp);

  /* Initialise and fetch the raw new frame row */

  src_buffer = gimp_drawable_get_buffer (drawable_ID);

  gegl_buffer_get (src_buffer, GEGL_RECTANGLE (0, row_num - rawy,
                                               rawwidth, 1), 1.0,
                   format, line_buf,
                   GEGL_AUTO_ROWSTRIDE, GEGL_ABYSS_NONE);

  g_object_unref (src_buffer);

  /* render... */

  srcptr = line_buf;

  for (i=rawx; i<rawwidth+rawx; i++)
    {
      if (i>=0 && i<dest_width)
        {
          if ((!has_alpha) || ((*(srcptr+rawbpp-1))&128))
            {
              gint pi;

              for (pi = 0; pi < pixelstep-1; pi++)
                {
                  dest[i*pixelstep +pi] = *(srcptr + pi);
                }

              dest[i*pixelstep + pixelstep - 1] = 255;
            }
        }

      srcptr += rawbpp;
    }
}


static gint32
do_optimizations (GimpRunMode run_mode,
                  gboolean    diff_only)
{
  static guchar *rawframe = NULL;
  guchar        *srcptr;
  guchar        *destptr;
  gint           row, this_frame_num;
  guint32        frame_sizebytes;
  gint32         new_layer_id;
  DisposeType    dispose;
  guchar        *this_frame = NULL;
  guchar        *last_frame = NULL;
  guchar        *opti_frame = NULL;
  guchar        *back_frame = NULL;

  gint           this_delay;
  gint           cumulated_delay = 0;
  gint           last_true_frame = -1;
  gint           buflen;

  gchar         *oldlayer_name;
  gchar         *newlayer_name;

  gboolean       can_combine;

  gint32         bbox_top, bbox_bottom, bbox_left, bbox_right;
  gint32         rbox_top, rbox_bottom, rbox_left, rbox_right;

  switch (opmode)
    {
    case OPUNOPTIMIZE:
      gimp_progress_init (_("Unoptimizing animation"));
      break;
    case OPFOREGROUND:
      gimp_progress_init (_("Removing animation background"));
      break;
    case OPBACKGROUND:
      gimp_progress_init (_("Finding animation background"));
      break;
    case OPOPTIMIZE:
    default:
      gimp_progress_init (_("Optimizing animation"));
      break;
    }

  width     = gimp_image_width (image_id);
  height    = gimp_image_height (image_id);
  layers    = gimp_image_get_layers (image_id, &total_frames);
  imagetype = gimp_image_base_type (image_id);
  pixelstep = (imagetype == GIMP_RGB) ? 4 : 2;

  drawabletype_alpha = (imagetype == GIMP_RGB) ? GIMP_RGBA_IMAGE :
    ((imagetype == GIMP_INDEXED) ? GIMP_INDEXEDA_IMAGE : GIMP_GRAYA_IMAGE);

  frame_sizebytes = width * height * pixelstep;

  this_frame = g_malloc (frame_sizebytes);
  last_frame = g_malloc (frame_sizebytes);
  opti_frame = g_malloc (frame_sizebytes);

  if (opmode == OPBACKGROUND ||
      opmode == OPFOREGROUND)
    back_frame = g_malloc (frame_sizebytes);

  total_alpha (this_frame, width*height, pixelstep);
  total_alpha (last_frame, width*height, pixelstep);

  new_image_id = gimp_image_new(width, height, imagetype);
  gimp_image_undo_disable (new_image_id);

  if (imagetype == GIMP_INDEXED)
    {
      palette = gimp_image_get_colormap (image_id, &ncolors);
      gimp_image_set_colormap (new_image_id, palette, ncolors);
    }

#if 1
  if (opmode == OPBACKGROUND ||
      opmode == OPFOREGROUND)
    {
      /* iterate through all rows of all frames, find statistical
         mode for each pixel position. */
      gint     i,j;
      guchar **these_rows;
      guchar **red;
      guchar **green;
      guchar **blue;
      guint  **count;
      guint   *num_colors;

      these_rows = g_new (guchar *, total_frames);
      red =        g_new (guchar *, total_frames);
      green =      g_new (guchar *, total_frames);
      blue =       g_new (guchar *, total_frames);
      count =      g_new (guint *, total_frames);

      num_colors = g_new (guint, width);

      for (this_frame_num=0; this_frame_num<total_frames; this_frame_num++)
        {
          these_rows[this_frame_num] = g_malloc(width * pixelstep);

          red[this_frame_num]   = g_new (guchar, width);
          green[this_frame_num] = g_new (guchar, width);
          blue[this_frame_num]  = g_new (guchar, width);

          count[this_frame_num] = g_new0(guint, width);
        }

      for (row = 0; row < height; row++)
        {
          memset(num_colors, 0, width * sizeof(guint));

          for (this_frame_num=0; this_frame_num<total_frames; this_frame_num++)
            {
              gint32 drawable_ID = layers[total_frames-(this_frame_num+1)];

              dispose = get_frame_disposal (this_frame_num);

              compose_row (this_frame_num,
                           dispose,
                           row,
                           these_rows[this_frame_num],
                           width,
                           drawable_ID,
                           FALSE);
            }

          for (this_frame_num=0; this_frame_num<total_frames; this_frame_num++)
            {
              for (i=0; i<width; i++)
                {
                  if (these_rows[this_frame_num][i * pixelstep + pixelstep -1]
                      >= 128)
                    {
                      for (j=0; j<num_colors[i]; j++)
                        {

                          switch (pixelstep)
                            {
                            case 4:
                              if (these_rows[this_frame_num][i * 4 +0] ==
                                  red[j][i] &&
                                  these_rows[this_frame_num][i * 4 +1] ==
                                  green[j][i] &&
                                  these_rows[this_frame_num][i * 4 +2] ==
                                  blue[j][i])
                                {
                                  (count[j][i])++;
                                  goto same;
                                }
                              break;
                            case 2:
                              if (these_rows[this_frame_num][i * 2 +0] ==
                                  red[j][i])
                                {
                                  (count[j][i])++;
                                  goto same;
                                }
                              break;
                            default:
                              g_error ("Eeep!");
                              break;
                            }
                        }

                      count[num_colors[i]][i] = 1;
                      red[num_colors[i]][i] =
                        these_rows[this_frame_num][i * pixelstep];
                      if (pixelstep == 4)
                        {
                          green[num_colors[i]][i] =
                            these_rows[this_frame_num][i * 4 +1];
                          blue[num_colors[i]][i] =
                            these_rows[this_frame_num][i * 4 +2];
                        }
                      num_colors[i]++;
                    }
                same:
                  /* nop */;
                }
            }

          for (i=0; i<width; i++)
            {
              guint  best_count = 0;
              guchar best_r = 255, best_g = 0, best_b = 255;

              for (j=0; j<num_colors[i]; j++)
                {
                  if (count[j][i] > best_count)
                    {
                      best_count = count[j][i];
                      best_r = red[j][i];
                      best_g = green[j][i];
                      best_b = blue[j][i];
                    }
                }

              back_frame[width * pixelstep * row +i*pixelstep + 0] = best_r;
              if (pixelstep == 4)
                {
                  back_frame[width * pixelstep * row +i*pixelstep + 1] =
                    best_g;
                  back_frame[width * pixelstep * row +i*pixelstep + 2] =
                    best_b;
                }
              back_frame[width * pixelstep * row +i*pixelstep +pixelstep-1] =
                (best_count == 0) ? 0 : 255;

              if (best_count == 0)
                g_warning("yayyyy!");
            }
          /*      memcpy(&back_frame[width * pixelstep * row],
                  these_rows[0],
                  width * pixelstep);*/
        }

      for (this_frame_num=0; this_frame_num<total_frames; this_frame_num++)
        {
          g_free (these_rows[this_frame_num]);
          g_free (red[this_frame_num]);
          g_free (green[this_frame_num]);
          g_free (blue[this_frame_num]);
          g_free (count[this_frame_num]);
        }

      g_free (these_rows);
      g_free (red);
      g_free (green);
      g_free (blue);
      g_free (count);
      g_free (num_colors);
    }
#endif

  if (opmode == OPBACKGROUND)
    {
      GeglBuffer *buffer;
      const Babl *format;

      new_layer_id = gimp_layer_new (new_image_id,
                                     "Backgroundx",
                                     width, height,
                                     drawabletype_alpha,
                                     100.0,
                                     gimp_image_get_default_new_layer_mode (new_image_id));

      gimp_image_insert_layer (new_image_id, new_layer_id, -1, 0);

      buffer = gimp_drawable_get_buffer (new_layer_id);

      format = get_format (new_layer_id);

      gegl_buffer_set (buffer, GEGL_RECTANGLE (0, 0, width, height), 0,
                       format, back_frame,
                       GEGL_ABYSS_NONE);

      g_object_unref (buffer);
    }
  else
    {
      for (this_frame_num=0; this_frame_num<total_frames; this_frame_num++)
        {
          /*
           * BUILD THIS FRAME into our 'this_frame' buffer.
           */

          gint32 drawable_ID = layers[total_frames-(this_frame_num+1)];

          /* Image has been closed/etc since we got the layer list? */
          /* FIXME - How do we tell if a gimp_drawable_get() fails? */
          if (gimp_drawable_width (drawable_ID) == 0)
            {
              gimp_quit ();
            }

          this_delay = get_frame_duration (this_frame_num);
          dispose    = get_frame_disposal (this_frame_num);

          for (row = 0; row < height; row++)
            {
              compose_row (this_frame_num,
                           dispose,
                           row,
                           &this_frame[pixelstep*width * row],
                           width,
                           drawable_ID,
                           FALSE
                           );
            }

          if (opmode == OPFOREGROUND)
            {
              gint xit, yit, byteit;

              for (yit=0; yit<height; yit++)
                {
                  for (xit=0; xit<width; xit++)
                    {
                      for (byteit=0; byteit<pixelstep-1; byteit++)
                        {
                          if (back_frame[yit*width*pixelstep + xit*pixelstep
                                        + byteit]
                              !=
                              this_frame[yit*width*pixelstep + xit*pixelstep
                                        + byteit])
                            {
                              goto enough;
                            }
                        }
                      this_frame[yit*width*pixelstep + xit*pixelstep
                                + pixelstep - 1] = 0;
                    enough:
                      /* nop */;
                    }
                }
            }

          can_combine = FALSE;
          bbox_left   = 0;
          bbox_top    = 0;
          bbox_right  = width;
          bbox_bottom = height;
          rbox_left   = 0;
          rbox_top    = 0;
          rbox_right  = width;
          rbox_bottom = height;

          /* copy 'this' frame into a buffer which we can safely molest */
          memcpy (opti_frame, this_frame, frame_sizebytes);
          /*
           *
           * OPTIMIZE HERE!
           *
           */
          if (
              (this_frame_num != 0) /* Can't delta bottom frame! */
              && (opmode == OPOPTIMIZE)
              )
            {
              gint xit, yit, byteit;

              can_combine = TRUE;

              /*
               * SEARCH FOR BOUNDING BOX
               */
              bbox_left   = width;
              bbox_top    = height;
              bbox_right  = 0;
              bbox_bottom = 0;
              rbox_left   = width;
              rbox_top    = height;
              rbox_right  = 0;
              rbox_bottom = 0;

              for (yit=0; yit<height; yit++)
                {
                  for (xit=0; xit<width; xit++)
                    {
                      gboolean keep_pix;
                      gboolean opaq_pix;

                      /* Check if 'this' and 'last' are transparent */
                      if (!(this_frame[yit*width*pixelstep + xit*pixelstep
                                      + pixelstep-1]&128)
                          &&
                          !(last_frame[yit*width*pixelstep + xit*pixelstep
                                      + pixelstep-1]&128))
                        {
                          keep_pix = FALSE;
                          opaq_pix = FALSE;
                          goto decided;
                        }
                      /* Check if just 'this' is transparent */
                      if ((last_frame[yit*width*pixelstep + xit*pixelstep
                                     + pixelstep-1]&128)
                          &&
                          !(this_frame[yit*width*pixelstep + xit*pixelstep
                                      + pixelstep-1]&128))
                        {
                          keep_pix = TRUE;
                          opaq_pix = FALSE;
                          can_combine = FALSE;
                          goto decided;
                        }
                      /* Check if just 'last' is transparent */
                      if (!(last_frame[yit*width*pixelstep + xit*pixelstep
                                      + pixelstep-1]&128)
                          &&
                          (this_frame[yit*width*pixelstep + xit*pixelstep
                                     + pixelstep-1]&128))
                        {
                          keep_pix = TRUE;
                          opaq_pix = TRUE;
                          goto decided;
                        }
                      /* If 'last' and 'this' are opaque, we have
                       *  to check if they're the same color - we
                       *  only have to keep the pixel if 'last' or
                       *  'this' are opaque and different.
                       */
                      keep_pix = FALSE;
                      opaq_pix = TRUE;
                      for (byteit=0; byteit<pixelstep-1; byteit++)
                        {
                          if ((last_frame[yit*width*pixelstep + xit*pixelstep
                                         + byteit]
                               !=
                               this_frame[yit*width*pixelstep + xit*pixelstep
                                         + byteit])
                              )
                            {
                              keep_pix = TRUE;
                              goto decided;
                            }
                        }
                    decided:
                      if (opaq_pix)
                        {
                          if (xit<rbox_left) rbox_left=xit;
                          if (xit>rbox_right) rbox_right=xit;
                          if (yit<rbox_top) rbox_top=yit;
                          if (yit>rbox_bottom) rbox_bottom=yit;
                        }
                      if (keep_pix)
                        {
                          if (xit<bbox_left) bbox_left=xit;
                          if (xit>bbox_right) bbox_right=xit;
                          if (yit<bbox_top) bbox_top=yit;
                          if (yit>bbox_bottom) bbox_bottom=yit;
                        }
                      else
                        {
                          /* pixel didn't change this frame - make
                           *  it transparent in our optimized buffer!
                           */
                          opti_frame[yit*width*pixelstep + xit*pixelstep
                                    + pixelstep-1] = 0;
                        }
                    } /* xit */
                } /* yit */

              if (!can_combine)
                {
                  bbox_left = rbox_left;
                  bbox_top = rbox_top;
                  bbox_right = rbox_right;
                  bbox_bottom = rbox_bottom;
                }

              bbox_right++;
              bbox_bottom++;

              if (can_combine && !diff_only)
                {
                  /* Try to optimize the pixel data for RLE or LZW compression
                   * by making some transparent pixels non-transparent if they
                   * would have the same color as the adjacent pixels.  This
                   * gives a better compression if the algorithm compresses
                   * the image line by line.
                   * See: http://bugzilla.gnome.org/show_bug.cgi?id=66367
                   * It may not be very efficient to add two additional passes
                   * over the pixels, but this hopefully makes the code easier
                   * to maintain and less error-prone.
                   */
                  for (yit = bbox_top; yit < bbox_bottom; yit++)
                    {
                      /* Compare with previous pixels from left to right */
                      for (xit = bbox_left + 1; xit < bbox_right; xit++)
                        {
                          if (!(opti_frame[yit*width*pixelstep
                                           + xit*pixelstep
                                           + pixelstep-1]&128)
                              && (opti_frame[yit*width*pixelstep
                                             + (xit-1)*pixelstep
                                             + pixelstep-1]&128)
                              && (last_frame[yit*width*pixelstep
                                             + xit*pixelstep
                                             + pixelstep-1]&128))
                            {
                              for (byteit=0; byteit<pixelstep-1; byteit++)
                                {
                                  if (opti_frame[yit*width*pixelstep
                                                 + (xit-1)*pixelstep
                                                 + byteit]
                                      !=
                                      last_frame[yit*width*pixelstep
                                                 + xit*pixelstep
                                                 + byteit])
                                    {
                                      goto skip_right;
                                    }
                                }
                              /* copy the color and alpha */
                              for (byteit=0; byteit<pixelstep; byteit++)
                                {
                                  opti_frame[yit*width*pixelstep
                                             + xit*pixelstep
                                             + byteit]
                                    = last_frame[yit*width*pixelstep
                                                 + xit*pixelstep
                                                 + byteit];
                                }
                            }
                        skip_right:
                          /* nop */;
                        } /* xit */

                      /* Compare with next pixels from right to left */
                      for (xit = bbox_right - 2; xit >= bbox_left; xit--)
                        {
                          if (!(opti_frame[yit*width*pixelstep
                                           + xit*pixelstep
                                           + pixelstep-1]&128)
                              && (opti_frame[yit*width*pixelstep
                                             + (xit+1)*pixelstep
                                             + pixelstep-1]&128)
                              && (last_frame[yit*width*pixelstep
                                             + xit*pixelstep
                                             + pixelstep-1]&128))
                            {
                              for (byteit=0; byteit<pixelstep-1; byteit++)
                                {
                                  if (opti_frame[yit*width*pixelstep
                                                 + (xit+1)*pixelstep
                                                 + byteit]
                                      !=
                                      last_frame[yit*width*pixelstep
                                                 + xit*pixelstep
                                                 + byteit])
                                    {
                                      goto skip_left;
                                    }
                                }
                              /* copy the color and alpha */
                              for (byteit=0; byteit<pixelstep; byteit++)
                                {
                                  opti_frame[yit*width*pixelstep
                                             + xit*pixelstep
                                             + byteit]
                                    = last_frame[yit*width*pixelstep
                                                 + xit*pixelstep
                                                 + byteit];
                                }
                            }
                        skip_left:
                          /* nop */;
                        } /* xit */
                    } /* yit */
                }

              /*
               * Collapse opti_frame data down such that the data
               *  which occupies the bounding box sits at the start
               *  of the data (for convenience with ..set_rect()).
               */
              destptr = opti_frame;
              /*
               * If can_combine, then it's safe to use our optimized
               *  alpha information.  Otherwise, an opaque pixel became
               *  transparent this frame, and we'll have to use the
               *  actual true frame's alpha.
               */
              if (can_combine)
                srcptr = opti_frame;
              else
                srcptr = this_frame;
              for (yit=bbox_top; yit<bbox_bottom; yit++)
                {
                  for (xit=bbox_left; xit<bbox_right; xit++)
                    {
                      for (byteit=0; byteit<pixelstep; byteit++)
                        {
                          *(destptr++) = srcptr[yit*pixelstep*width +
                                               pixelstep*xit + byteit];
                        }
                    }
                }
            } /* !bot frame? */
          else
            {
              memcpy (opti_frame, this_frame, frame_sizebytes);
            }

          /*
           *
           * REMEMBER THE ANIMATION STATUS TO DELTA AGAINST NEXT TIME
           *
           */
          memcpy (last_frame, this_frame, frame_sizebytes);


          /*
           *
           * PUT THIS FRAME INTO A NEW LAYER IN THE NEW IMAGE
           *
           */

          oldlayer_name =
            gimp_item_get_name(layers[total_frames-(this_frame_num+1)]);

          buflen = strlen(oldlayer_name) + 40;

          newlayer_name = g_malloc(buflen);

          remove_disposal_tag(newlayer_name, oldlayer_name);
          g_free(oldlayer_name);

          oldlayer_name = g_malloc(buflen);

          remove_ms_tag(oldlayer_name, newlayer_name);

          g_snprintf(newlayer_name, buflen, "%s(%dms)%s",
                     oldlayer_name, this_delay,
                     (this_frame_num ==  0) ? "" :
                     can_combine ? "(combine)" : "(replace)");

          g_free(oldlayer_name);

          /* Empty frame! */
          if (bbox_right <= bbox_left ||
              bbox_bottom <= bbox_top)
            {
              cumulated_delay += this_delay;

              g_free (newlayer_name);

              oldlayer_name = gimp_item_get_name (last_true_frame);

              buflen = strlen (oldlayer_name) + 40;

              newlayer_name = g_malloc (buflen);

              remove_disposal_tag (newlayer_name, oldlayer_name);
              g_free (oldlayer_name);

              oldlayer_name = g_malloc (buflen);

              remove_ms_tag (oldlayer_name, newlayer_name);

              g_snprintf (newlayer_name, buflen, "%s(%dms)%s",
                          oldlayer_name, cumulated_delay,
                          (this_frame_num ==  0) ? "" :
                          can_combine ? "(combine)" : "(replace)");

              gimp_item_set_name (last_true_frame, newlayer_name);

              g_free (newlayer_name);
            }
          else
            {
              GeglBuffer *buffer;
              const Babl *format;

              cumulated_delay = this_delay;

              last_true_frame =
                new_layer_id = gimp_layer_new (new_image_id,
                                               newlayer_name,
                                               bbox_right-bbox_left,
                                               bbox_bottom-bbox_top,
                                               drawabletype_alpha,
                                               100.0,
                                               gimp_image_get_default_new_layer_mode (new_image_id));
              g_free (newlayer_name);

              gimp_image_insert_layer (new_image_id, new_layer_id, -1, 0);

              buffer = gimp_drawable_get_buffer (new_layer_id);

              format = get_format (new_layer_id);

              gegl_buffer_set (buffer,
                               GEGL_RECTANGLE (0, 0,
                                               bbox_right-bbox_left,
                                               bbox_bottom-bbox_top), 0,
                               format, opti_frame,
                               GEGL_AUTO_ROWSTRIDE);

              g_object_unref (buffer);
              gimp_item_transform_translate (new_layer_id, bbox_left, bbox_top);
            }

          gimp_progress_update (((gdouble) this_frame_num + 1.0) /
                                ((gdouble) total_frames));
        }

      gimp_progress_update (1.0);
    }

  gimp_image_undo_enable (new_image_id);

  if (run_mode != GIMP_RUN_NONINTERACTIVE)
    gimp_display_new (new_image_id);

  g_free (rawframe);
  rawframe = NULL;

  g_free (last_frame);
  last_frame = NULL;

  g_free (this_frame);
  this_frame = NULL;

  g_free (opti_frame);
  opti_frame = NULL;

  g_free (back_frame);
  back_frame = NULL;

  return new_image_id;
}

/* Util. */

static DisposeType
get_frame_disposal (guint whichframe)
{
  gchar       *layer_name;
  DisposeType  disposal;

  layer_name = gimp_item_get_name(layers[total_frames-(whichframe+1)]);
  disposal = parse_disposal_tag(layer_name);
  g_free(layer_name);

  return disposal;
}

static guint32
get_frame_duration (guint whichframe)
{
  gchar* layer_name;
  gint   duration = 0;

  layer_name = gimp_item_get_name(layers[total_frames-(whichframe+1)]);
  if (layer_name)
    {
      duration = parse_ms_tag(layer_name);
      g_free(layer_name);
    }

  if (duration < 0) duration = 100;  /* FIXME for default-if-not-said  */
  if (duration == 0) duration = 100; /* FIXME - 0-wait is nasty */

  return (guint32) duration;
}

static gboolean
is_ms_tag (const gchar *str,
           gint        *duration,
           gint        *taglength)
{
  gint sum = 0;
  gint offset;
  gint length;

  length = strlen(str);

  if (str[0] != '(')
    return FALSE;

  offset = 1;

  /* eat any spaces between open-parenthesis and number */
  while ((offset<length) && (str[offset] == ' '))
    offset++;

  if ((offset>=length) || (!g_ascii_isdigit (str[offset])))
    return 0;

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

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

  /* eat any spaces between number and 'ms' */
  while ((offset<length) && (str[offset] == ' '))
    offset++;

  if ((length-offset <= 2) ||
      (g_ascii_toupper (str[offset]) != 'M') ||
      (g_ascii_toupper (str[offset+1]) != 'S'))
    return FALSE;

  offset += 2;

  /* eat any spaces between 'ms' and close-parenthesis */
  while ((offset<length) && (str[offset] == ' '))
    offset++;

  if ((length-offset < 1) || (str[offset] != ')'))
    return FALSE;

  offset++;

  *duration  = sum;
  *taglength = offset;

  return TRUE;
}

static int
parse_ms_tag (const char *str)
{
  gint i;
  gint rtn;
  gint dummy;
  gint length;

  length = strlen (str);

  for (i = 0; i < length; i++)
    {
      if (is_ms_tag (&str[i], &rtn, &dummy))
        return rtn;
    }

  return -1;
}

static gboolean
is_disposal_tag (const gchar *str,
                 DisposeType *disposal,
                 gint        *taglength)
{
  if (strlen (str) != 9)
    return FALSE;

  if (strncmp (str, "(combine)", 9) == 0)
    {
      *taglength = 9;
      *disposal = DISPOSE_COMBINE;
      return TRUE;
    }
  else if (strncmp (str, "(replace)", 9) == 0)
    {
      *taglength = 9;
      *disposal = DISPOSE_REPLACE;
      return TRUE;
    }

  return FALSE;
}


static DisposeType
parse_disposal_tag (const gchar *str)
{
  DisposeType rtn;
  gint        i, dummy;
  gint        length;

  length = strlen(str);

  for (i=0; i<length; i++)
    {
      if (is_disposal_tag (&str[i], &rtn, &dummy))
        {
          return rtn;
        }
    }

  return DISPOSE_UNDEFINED; /* FIXME */
}

static void
remove_disposal_tag (gchar *dest,
                     gchar *src)
{
  gint        offset = 0;
  gint        destoffset = 0;
  gint        length;
  int         taglength;
  DisposeType dummy;

  length = strlen(src);

  strcpy(dest, src);

  while (offset<=length)
    {
      if (is_disposal_tag(&src[offset], &dummy, &taglength))
        {
          offset += taglength;
        }
      dest[destoffset] = src[offset];
      destoffset++;
      offset++;
    }

  dest[offset] = '\0';
}

static void
remove_ms_tag (gchar *dest,
               gchar *src)
{
  gint offset = 0;
  gint destoffset = 0;
  gint length;
  gint taglength;
  gint dummy;

  length = strlen(src);

  strcpy(dest, src);

  while (offset<=length)
    {
      if (is_ms_tag(&src[offset], &dummy, &taglength))
        {
          offset += taglength;
        }
      dest[destoffset] = src[offset];
      destoffset++;
      offset++;
    }

  dest[offset] = '\0';
}