file-mng.c

/* GIMP - The GNU Image Manipulation Program
 * Copyright (C) 1995 Spencer Kimball and Peter Mattis
 *
 * Multiple-image Network Graphics (MNG) plug-in
 *
 * Copyright (C) 2002 Mukund Sivaraman <muks@mukund.org>
 * Portions are copyright of the authors of the file-gif-save, file-png-save
 * and file-jpeg-save plug-ins' code. The exact ownership of these code
 * fragments has not been determined.
 *
 * This work was sponsored by Xinit Systems Limited, UK.
 * http://www.xinitsystems.com/
 *
 * 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 <http://www.gnu.org/licenses/>.
 * --
 *
 * For now, this MNG plug-in can only save images. It cannot load images.
 * Save your working copy as .xcf and use this for "exporting" your images
 * to MNG. Supports animation the same way as animated GIFs. Supports alpha
 * transparency. Uses the libmng library (http://www.libmng.com/).
 * The MIME content-type for MNG images is video/x-mng for now. Make sure
 * your web-server is configured appropriately if you want to serve MNG
 * images.
 *
 * Since libmng cannot write PNG, JNG and delta PNG chunks at this time
 * (when this text was written), this plug-in uses libpng and jpeglib to
 * create the data for the chunks.
 *
 */

#include "config.h"

#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

#include <glib/gstdio.h>

#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif


/* libpng and jpeglib are currently used in this plug-in. */

#include <png.h>
#include <jpeglib.h>


/* Grrr. The grrr is because the following have to be defined
 * by the application as well for some reason, although they
 * were enabled when libmng was compiled. The authors of libmng
 * must look into this. */

#if !defined(MNG_SUPPORT_FULL)
#define MNG_SUPPORT_FULL 1
#endif

#if !defined(MNG_SUPPORT_READ)
#define MNG_SUPPORT_READ 1
#endif

#if !defined(MNG_SUPPORT_WRITE)
#define MNG_SUPPORT_WRITE 1
#endif

#if !defined(MNG_SUPPORT_DISPLAY)
#define MNG_SUPPORT_DISPLAY 1
#endif

#if !defined(MNG_ACCESS_CHUNKS)
#define MNG_ACCESS_CHUNKS 1
#endif

#include <libmng.h>

#include "libgimp/gimp.h"
#include "libgimp/gimpui.h"

#include "libgimp/stdplugins-intl.h"


#define SAVE_PROC      "file-mng-save"
#define PLUG_IN_BINARY "file-mng"
#define PLUG_IN_ROLE   "gimp-file-mng"
#define SCALE_WIDTH    125

enum
{
  CHUNKS_PNG_D,
  CHUNKS_JNG_D,
  CHUNKS_PNG,
  CHUNKS_JNG
};

enum
{
  DISPOSE_COMBINE,
  DISPOSE_REPLACE
};


/* The contents of this struct remain static among multiple
 * invocations of the plug-in. */

/* TODO: describe the members of the struct */

struct mng_data_t
{
  gint32 interlaced;
  gint32 bkgd;
  gint32 gama;
  gint32 phys;
  gint32 time;
  gint32 default_chunks;

  gfloat quality;
  gfloat smoothing;

  gint32 compression_level;

  gint32 loop;
  gint32 default_delay;
  gint32 default_dispose;
};

/* Values of the instance of the above struct when the plug-in is
 * first invoked. */

static struct mng_data_t mng_data =
{
  FALSE,                        /* interlaced */
  FALSE,                        /* bkgd */
  FALSE,                        /* gama */
  TRUE,                         /* phys */
  TRUE,                         /* time */
  CHUNKS_PNG_D,                 /* default_chunks */

  0.75,                         /* quality */
  0.0,                          /* smoothing */

  9,                            /* compression_level */

  TRUE,                         /* loop */
  100,                          /* default_delay */
  DISPOSE_COMBINE               /* default_dispose */
};


/* These are not saved or restored. */

struct mng_globals_t
{
  gboolean   has_trns;
  png_bytep  trans;
  int        num_trans;
  gboolean   has_plte;
  png_colorp palette;
  int        num_palette;
};

static struct mng_globals_t mngg;


/* The output FILE pointer which is used by libmng;
 * passed around as user data. */
struct mnglib_userdata_t
{
  FILE *fp;
};


/*
 * Function prototypes
 */

static mng_ptr   myalloc       (mng_size_t  size);
static void      myfree        (mng_ptr     ptr,
                                mng_size_t  size);
static mng_bool  myopenstream  (mng_handle  handle);
static mng_bool  myclosestream (mng_handle  handle);
static mng_bool  mywritedata   (mng_handle  handle,
                                mng_ptr     buf,
                                mng_uint32  size,
                                mng_uint32 *written_size);


static gint32    parse_chunks_type_from_layer_name   (const gchar *str);
static gint32    parse_disposal_type_from_layer_name (const gchar *str);
static gint32    parse_ms_tag_from_layer_name        (const gchar *str);
static gint      find_unused_ia_colour               (guchar      *pixels,
                                                      gint         numpixels,
                                                      gint        *colors);
static gboolean  ia_has_transparent_pixels           (guchar      *pixels,
                                                      gint         numpixels);

static gboolean  respin_cmap     (png_structp       png_ptr,
                                  png_infop         png_info_ptr,
                                  guchar           *remap,
                                  gint32            image_id,
                                  GimpDrawable     *drawable,
                                  int              *bit_depth);

static gboolean  mng_save_image  (const gchar      *filename,
                                  gint32            image_id,
                                  gint32            drawable_id,
                                  gint32            original_image_id,
                                  GError          **error);
static gboolean  mng_save_dialog (gint32            image_id);

static void      query           (void);
static void      run             (const gchar      *name,
                                  gint              nparams,
                                  const GimpParam  *param,
                                  gint             *nreturn_vals,
                                  GimpParam       **return_vals);


/*
 * Callbacks for libmng
 */

static mng_ptr
myalloc (mng_size_t size)
{
  gpointer ptr;

  ptr = g_try_malloc (size);

  if (ptr != NULL)
    memset (ptr, 0, size);

  return ((mng_ptr) ptr);
}

static void
myfree (mng_ptr    ptr,
        mng_size_t size)
{
  g_free (ptr);
}

static mng_bool
myopenstream (mng_handle handle)
{
  return MNG_TRUE;
}

static mng_bool
myclosestream (mng_handle handle)
{
  return MNG_TRUE;
}

static mng_bool
mywritedata (mng_handle  handle,
             mng_ptr     buf,
             mng_uint32  size,
             mng_uint32 *written_size)
{
  struct mnglib_userdata_t *userdata =
    (struct mnglib_userdata_t *) mng_get_userdata (handle);


  *written_size = (mng_uint32) fwrite ((void *) buf, 1,
                                       (size_t) size, userdata->fp);

  return MNG_TRUE;
}


/* Parses which output chunk type to use for this layer
 * from the layer name. */

static gint32
parse_chunks_type_from_layer_name (const gchar *str)
{
  guint i;

  for (i = 0; (i + 5) <= strlen (str); i++)
    {
      if (g_ascii_strncasecmp (str + i, "(png)", 5) == 0)
        return CHUNKS_PNG;
      else if (g_ascii_strncasecmp (str + i, "(jng)", 5) == 0)
        return CHUNKS_JNG;
    }

  return mng_data.default_chunks;
}


/* Parses which disposal type to use for this layer
 * from the layer name. */

static gint32
parse_disposal_type_from_layer_name (const gchar *str)
{
  guint i;

  for (i = 0; (i + 9) <= strlen (str); i++)
    {
      if (g_ascii_strncasecmp (str + i, "(combine)", 9) == 0)
        return DISPOSE_COMBINE;
      else if (g_ascii_strncasecmp (str + i, "(replace)", 9) == 0)
        return DISPOSE_REPLACE;
    }

  return mng_data.default_dispose;
}


/* Parses the millisecond delay to use for this layer
 * from the layer name. */

static gint32
parse_ms_tag_from_layer_name (const gchar *str)
{
  guint offset = 0;
  gint32 sum = 0;
  guint length = strlen (str);

  while (TRUE)
    {
      while ((offset < length) && (str[offset] != '('))
        offset++;

      if (offset >= length)
        return mng_data.default_delay;

      offset++;

      if (g_ascii_isdigit (str[offset]))
        break;
    }

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

  if ((length - offset) <= 2)
    return mng_data.default_delay;

  if ((g_ascii_toupper (str[offset]) != 'M') ||
      (g_ascii_toupper (str[offset + 1]) != 'S'))
    return mng_data.default_delay;

  return sum;
}


/* Try to find a colour in the palette which isn't actually
 * used in the image, so that we can use it as the transparency
 * index. Taken from png.c */
static gint
find_unused_ia_colour (guchar *pixels,
                       gint    numpixels,
                       gint   *colors)
{
  gint     i;
  gboolean ix_used[256];
  gboolean trans_used = FALSE;

  for (i = 0; i < *colors; i++)
    {
      ix_used[i] = FALSE;
    }

  for (i = 0; i < numpixels; i++)
    {
      /* If alpha is over a threshold, the colour index in the
       * palette is taken. Otherwise, this pixel is transparent. */
      if (pixels[i * 2 + 1] > 127)
        ix_used[pixels[i * 2]] = TRUE;
      else
        trans_used = TRUE;
    }

  /* If there is no transparency, ignore alpha. */
  if (trans_used == FALSE)
    return -1;

  for (i = 0; i < *colors; i++)
    {
      if (ix_used[i] == FALSE)
        {
          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)++;
      return ((*colors) - 1);
    }

  return -1;
}


static gboolean
ia_has_transparent_pixels (guchar *pixels,
                           gint    numpixels)
{
  while (numpixels --)
    {
      if (pixels [1] <= 127)
        return TRUE;
      pixels += 2;
    }
  return FALSE;
}

static int
get_bit_depth_for_palette (int num_palette)
{
  if (num_palette <= 2)
    return 1;
  else if (num_palette <= 4)
    return 2;
  else if (num_palette <= 16)
    return 4;
  else
    return 8;
}

/* Spins the color map (palette) putting the transparent color at
 * index 0 if there is space. If there isn't any space, warn the user
 * and forget about transparency. Returns TRUE if the colormap has
 * been changed and FALSE otherwise.
 */

static gboolean
respin_cmap (png_structp  pp,
             png_infop    info,
             guchar       *remap,
             gint32       image_id,
             GimpDrawable *drawable,
             int          *bit_depth)
{
  static guchar  trans[] = { 0 };
  guchar        *before;
  guchar        *pixels;
  gint           numpixels;
  gint           colors;
  gint           transparent;
  gint           cols, rows;
  GimpPixelRgn   pixel_rgn;

  before = gimp_image_get_colormap (image_id, &colors);

  /* Make sure there is something in the colormap */
  if (colors == 0)
    {
      before = g_new0 (guchar, 3);
      colors = 1;
    }

  cols      = drawable->width;
  rows      = drawable->height;
  numpixels = cols * rows;

  gimp_pixel_rgn_init (&pixel_rgn, drawable, 0, 0,
                       drawable->width, drawable->height, FALSE, FALSE);

  pixels = (guchar *) g_malloc (numpixels * 2);

  gimp_pixel_rgn_get_rect (&pixel_rgn, pixels, 0, 0,
                           drawable->width, drawable->height);

  if (ia_has_transparent_pixels (pixels, numpixels))
    {
      transparent = find_unused_ia_colour (pixels, numpixels, &colors);

      if (transparent != -1)
        {
          static png_color palette[256] = { {0, 0, 0} };
          gint i;

          /* Set tRNS chunk values for writing later. */
          mngg.has_trns = TRUE;
          mngg.trans = trans;
          mngg.num_trans = 1;

          /* Transform all pixels with a value = transparent to
           * 0 and vice versa to compensate for re-ordering in palette
           * due to png_set_tRNS().
           */

          remap[0] = transparent;
          remap[transparent] = 0;

          /* Copy from index 0 to index transparent - 1 to index 1 to
           * transparent of after, then from transparent+1 to colors-1
           * unchanged, and finally from index transparent to index 0.
           */

          for (i = 1; i < colors; i++)
            {
              palette[i].red = before[3 * remap[i]];
              palette[i].green = before[3 * remap[i] + 1];
              palette[i].blue = before[3 * remap[i] + 2];
            }

          /* Set PLTE chunk values for writing later. */
          mngg.has_plte = TRUE;
          mngg.palette = palette;
          mngg.num_palette = colors;

          *bit_depth = get_bit_depth_for_palette (colors);

          return TRUE;
        }
      else
        {
          g_message (_("Couldn't losslessly save transparency, "
                       "saving opacity instead."));
        }
    }

  mngg.has_plte = TRUE;
  mngg.palette = (png_colorp) before;
  mngg.num_palette = colors;
  *bit_depth = get_bit_depth_for_palette (colors);

  return FALSE;
}

static mng_retcode
mng_putchunk_plte_wrapper (mng_handle    handle,
                           gint          numcolors,
                           const guchar *colormap)
{
  mng_palette8 palette;

  memset (palette, 0, sizeof palette);
  if (0 < numcolors)
    memcpy (palette, colormap, numcolors * sizeof palette[0]);

  return mng_putchunk_plte (handle, numcolors, palette);
}

static mng_retcode
mng_putchunk_trns_wrapper (mng_handle    handle,
                           gint          n_alphas,
                           const guchar *buffer)
{
  const mng_bool mng_global = TRUE;
  const mng_bool mng_empty  = TRUE;
  mng_uint8arr   alphas;

  memset (alphas, 0, sizeof alphas);
  if (buffer && 0 < n_alphas)
    memcpy (alphas, buffer, n_alphas * sizeof alphas[0]);

  return mng_putchunk_trns (handle,
                            ! mng_empty,
                            ! mng_global,
                            MNG_COLORTYPE_INDEXED,
                            n_alphas,
                            alphas,
                            0, 0, 0, 0, 0, alphas);
}

static gboolean
mng_save_image (const gchar  *filename,
                gint32        image_id,
                gint32        drawable_id,
                gint32        original_image_id,
                GError      **error)
{
  gboolean        ret = FALSE;
  gint            rows, cols;
  volatile gint   i;
  time_t          t;
  struct tm      *gmt;

  gint            num_layers;
  gint32         *layers;

  struct mnglib_userdata_t *userdata;
  mng_handle      handle;
  guint32         mng_ticks_per_second;
  guint32         mng_simplicity_profile;

  layers = gimp_image_get_layers (image_id, &num_layers);

  if (num_layers < 1)
    return FALSE;

  if (num_layers > 1)
    mng_ticks_per_second = 1000;
  else
    mng_ticks_per_second = 0;

  rows = gimp_image_height (image_id);
  cols = gimp_image_width (image_id);

  mng_simplicity_profile = (MNG_SIMPLICITY_VALID |
                            MNG_SIMPLICITY_SIMPLEFEATURES |
                            MNG_SIMPLICITY_COMPLEXFEATURES);

  /* JNG and delta-PNG chunks exist */
  mng_simplicity_profile |= (MNG_SIMPLICITY_JNG |
                             MNG_SIMPLICITY_DELTAPNG);

  for (i = 0; i < num_layers; i++)
    if (gimp_drawable_has_alpha (layers[i]))
      {
        /* internal transparency exists */
        mng_simplicity_profile |= MNG_SIMPLICITY_TRANSPARENCY;

        /* validity of following flags */
        mng_simplicity_profile |= 0x00000040;

        /* semi-transparency exists */
        mng_simplicity_profile |= 0x00000100;

        /* background transparency should happen */
        mng_simplicity_profile |= 0x00000080;

        break;
      }

  userdata = g_new0 (struct mnglib_userdata_t, 1);
  userdata->fp = g_fopen (filename, "wb");

  if (NULL == userdata->fp)
    {
      g_set_error (error, G_FILE_ERROR, g_file_error_from_errno (errno),
                   _("Could not open '%s' for writing: %s"),
                   gimp_filename_to_utf8 (filename), g_strerror (errno));
      goto err;
    }

  handle = mng_initialize ((mng_ptr) userdata, myalloc, myfree, NULL);
  if (NULL == handle)
    {
      g_warning ("Unable to mng_initialize() in mng_save_image()");
      goto err2;
    }

  if ((mng_setcb_openstream (handle, myopenstream) != MNG_NOERROR) ||
      (mng_setcb_closestream (handle, myclosestream) != MNG_NOERROR) ||
      (mng_setcb_writedata (handle, mywritedata) != MNG_NOERROR))
    {
      g_warning ("Unable to setup callbacks in mng_save_image()");
      goto err3;
    }

  if (mng_create (handle) != MNG_NOERROR)
    {
      g_warning ("Unable to mng_create() image in mng_save_image()");
      goto err3;
    }

  if (mng_putchunk_mhdr (handle, cols, rows, mng_ticks_per_second, 1,
                         num_layers, mng_data.default_delay,
                         mng_simplicity_profile) != MNG_NOERROR)
    {
      g_warning ("Unable to mng_putchunk_mhdr() in mng_save_image()");
      goto err3;
    }

  if ((num_layers > 1) && (mng_data.loop))
    {
      gint32 ms =
        parse_ms_tag_from_layer_name (gimp_item_get_name (layers[0]));

      if (mng_putchunk_term (handle, MNG_TERMACTION_REPEAT,
                             MNG_ITERACTION_LASTFRAME,
                             ms, 0x7fffffff) != MNG_NOERROR)
        {
          g_warning ("Unable to mng_putchunk_term() in mng_save_image()");
          goto err3;
        }
    }
  else
    {
      gint32 ms =
        parse_ms_tag_from_layer_name (gimp_item_get_name (layers[0]));

      if (mng_putchunk_term (handle, MNG_TERMACTION_LASTFRAME,
                             MNG_ITERACTION_LASTFRAME,
                             ms, 0x7fffffff) != MNG_NOERROR)
        {
          g_warning ("Unable to mng_putchunk_term() in mng_save_image()");
          goto err3;
        }
    }


  /* For now, we hardwire a comment */

  if (mng_putchunk_text (handle,
                         strlen (MNG_TEXT_TITLE), MNG_TEXT_TITLE,
                         18, "Created using GIMP") != MNG_NOERROR)
    {
      g_warning ("Unable to mng_putchunk_text() in mng_save_image()");
      goto err3;
    }

#if 0

  /* how do we get this to work? */
  if (mng_data.bkgd)
    {
      GimpRGB bgcolor;
      guchar red, green, blue;

      gimp_context_get_background (&bgcolor);
      gimp_rgb_get_uchar (&bgcolor, &red, &green, &blue);

      if (mng_putchunk_back (handle, red, green, blue,
                             MNG_BACKGROUNDCOLOR_MANDATORY,
                             0, MNG_BACKGROUNDIMAGE_NOTILE) != MNG_NOERROR)
        {
          g_warning ("Unable to mng_putchunk_back() in mng_save_image()");
          goto err3;
        }

      if (mng_putchunk_bkgd (handle, MNG_FALSE, 2, 0,
                             gimp_rgb_luminance_uchar (&bgcolor),
                             red, green, blue) != MNG_NOERROR)
        {
          g_warning ("Unable to mng_putchunk_bkgd() in mng_save_image()");
          goto err3;
        }
    }

#endif

  if (mng_data.gama)
    {
      if (mng_putchunk_gama (handle, MNG_FALSE,
                             (1.0 / (gimp_gamma ()) * 100000)) != MNG_NOERROR)
        {
          g_warning ("Unable to mng_putchunk_gama() in mng_save_image()");
          goto err3;
        }
    }

#if 0

  /* how do we get this to work? */
  if (mng_data.phys)
    {
      gimp_image_get_resolution(original_image_id, &xres, &yres);

      if (mng_putchunk_phyg (handle, MNG_FALSE,
                             (mng_uint32) (xres * 39.37),
                             (mng_uint32) (yres * 39.37), 1) != MNG_NOERROR)
        {
          g_warning ("Unable to mng_putchunk_phyg() in mng_save_image()");
          goto err3;
        }

      if (mng_putchunk_phys (handle, MNG_FALSE,
                             (mng_uint32) (xres * 39.37),
                             (mng_uint32) (yres * 39.37), 1) != MNG_NOERROR)
        {
          g_warning ("Unable to mng_putchunk_phys() in mng_save_image()");
          goto err3;
        }
    }

#endif

  if (mng_data.time)
    {
      t = time (NULL);
      gmt = gmtime (&t);

      if (mng_putchunk_time (handle, gmt->tm_year + 1900, gmt->tm_mon + 1,
                             gmt->tm_mday, gmt->tm_hour, gmt->tm_min,
                             gmt->tm_sec) != MNG_NOERROR)
        {
          g_warning ("Unable to mng_putchunk_time() in mng_save_image()");
          goto err3;
        }
    }

  if (gimp_image_base_type (image_id) == GIMP_INDEXED)
    {
      guchar *palette;
      gint    numcolors;

      palette = gimp_image_get_colormap (image_id, &numcolors);

      if ((numcolors != 0) &&
          (mng_putchunk_plte_wrapper (handle, numcolors,
                                      palette) != MNG_NOERROR))
        {
          g_warning ("Unable to mng_putchunk_plte() in mng_save_image()");
          goto err3;
        }
    }

  for (i = (num_layers - 1); i >= 0; i--)
    {
      GimpImageType   layer_drawable_type;
      GimpDrawable   *layer_drawable;
      gint            layer_offset_x, layer_offset_y;
      gint            layer_rows, layer_cols;
      gchar          *layer_name;
      gint            layer_chunks_type;
      volatile gint   layer_bpp;
      GimpPixelRgn    layer_pixel_rgn;

      guint8          layer_mng_colortype;
      guint8          layer_mng_compression_type;
      guint8          layer_mng_interlace_type;
      gboolean        layer_has_unique_palette;

      gchar           frame_mode;
      int             frame_delay;
      gchar          *temp_file_name;
      png_structp     pp;
      png_infop       info;
      FILE           *infile, *outfile;
      int             num_passes;
      int             tile_height;
      guchar        **layer_pixels, *layer_pixel;
      int             pass, j, k, begin, end, num;
      guchar         *fixed;
      guchar          layer_remap[256];
      int             color_type;
      int             bit_depth;

      layer_name          = gimp_item_get_name (layers[i]);
      layer_chunks_type   = parse_chunks_type_from_layer_name (layer_name);
      layer_drawable_type = gimp_drawable_type (layers[i]);

      layer_drawable      = gimp_drawable_get (layers[i]);
      layer_rows          = layer_drawable->height;
      layer_cols          = layer_drawable->width;

      gimp_drawable_offsets (layers[i], &layer_offset_x, &layer_offset_y);
      layer_has_unique_palette = TRUE;

      for (j = 0; j < 256; j++)
        layer_remap[j] = j;

      switch (layer_drawable_type)
        {
        case GIMP_RGB_IMAGE:
          layer_bpp = 3;
          layer_mng_colortype = MNG_COLORTYPE_RGB;
          break;
        case GIMP_RGBA_IMAGE:
          layer_bpp = 4;
          layer_mng_colortype = MNG_COLORTYPE_RGBA;
          break;
        case GIMP_GRAY_IMAGE:
          layer_bpp = 1;
          layer_mng_colortype = MNG_COLORTYPE_GRAY;
          break;
        case GIMP_GRAYA_IMAGE:
          layer_bpp = 2;
          layer_mng_colortype = MNG_COLORTYPE_GRAYA;
          break;
        case GIMP_INDEXED_IMAGE:
          layer_bpp = 1;
          layer_mng_colortype = MNG_COLORTYPE_INDEXED;
          break;
        case GIMP_INDEXEDA_IMAGE:
          layer_bpp = 2;
          layer_mng_colortype = MNG_COLORTYPE_INDEXED | MNG_COLORTYPE_GRAYA;
          break;
        default:
          g_warning ("Unsupported GimpImageType in mng_save_image()");
          goto err3;
        }

      /* Delta PNG chunks are not yet supported */

      /* if (i == (num_layers - 1)) */
      {
        if (layer_chunks_type == CHUNKS_JNG_D)
          layer_chunks_type = CHUNKS_JNG;
        else if (layer_chunks_type == CHUNKS_PNG_D)
          layer_chunks_type = CHUNKS_PNG;
      }

      switch (layer_chunks_type)
        {
        case CHUNKS_PNG_D:
          layer_mng_compression_type = MNG_COMPRESSION_DEFLATE;
          if (mng_data.interlaced != 0)
            layer_mng_interlace_type = MNG_INTERLACE_ADAM7;
          else
            layer_mng_interlace_type = MNG_INTERLACE_NONE;
          break;
        case CHUNKS_JNG_D:
          layer_mng_compression_type = MNG_COMPRESSION_DEFLATE;
          if (mng_data.interlaced != 0)
            layer_mng_interlace_type = MNG_INTERLACE_ADAM7;
          else
            layer_mng_interlace_type = MNG_INTERLACE_NONE;
          break;
        case CHUNKS_PNG:
          layer_mng_compression_type = MNG_COMPRESSION_DEFLATE;
          if (mng_data.interlaced != 0)
            layer_mng_interlace_type = MNG_INTERLACE_ADAM7;
          else
            layer_mng_interlace_type = MNG_INTERLACE_NONE;
          break;
        case CHUNKS_JNG:
          layer_mng_compression_type = MNG_COMPRESSION_BASELINEJPEG;
          if (mng_data.interlaced != 0)
            layer_mng_interlace_type = MNG_INTERLACE_PROGRESSIVE;
          else
            layer_mng_interlace_type = MNG_INTERLACE_SEQUENTIAL;
          break;
        default:
          g_warning ("Huh? Programmer stupidity error "
                     "with 'layer_chunks_type'");
          goto err3;
        }

      if ((i == (num_layers - 1)) ||
          (parse_disposal_type_from_layer_name (layer_name) != DISPOSE_COMBINE))
        frame_mode = MNG_FRAMINGMODE_3;
      else
        frame_mode = MNG_FRAMINGMODE_1;

      frame_delay = parse_ms_tag_from_layer_name (layer_name);

      if (mng_putchunk_fram (handle, MNG_FALSE, frame_mode, 0, NULL,
                             MNG_CHANGEDELAY_DEFAULT,
                             MNG_CHANGETIMOUT_NO,
                             MNG_CHANGECLIPPING_DEFAULT,
                             MNG_CHANGESYNCID_NO,
                             frame_delay, 0, 0,
                             layer_offset_x,
                             layer_offset_x + layer_cols,
                             layer_offset_y,
                             layer_offset_y + layer_rows,
                             0, NULL) != MNG_NOERROR)
        {
          g_warning ("Unable to mng_putchunk_fram() in mng_save_image()");
          goto err3;
        }

      if ((layer_offset_x != 0) || (layer_offset_y != 0))
        {
          if (mng_putchunk_defi (handle, 0, 0, 1, 1, layer_offset_x,
                                 layer_offset_y, 1, layer_offset_x,
                                 layer_offset_x + layer_cols, layer_offset_y,
                                 layer_offset_y + layer_rows) != MNG_NOERROR)
            {
              g_warning ("Unable to mng_putchunk_defi() in mng_save_image()");
              goto err3;
            }
        }

      if ((temp_file_name = gimp_temp_name ("mng")) == NULL)
        {
          g_warning ("gimp_temp_name() failed in mng_save_image()");
          goto err3;
        }

      if ((outfile = g_fopen (temp_file_name, "wb")) == NULL)
        {
          g_set_error (error, G_FILE_ERROR, g_file_error_from_errno (errno),
                       _("Could not open '%s' for writing: %s"),
                       gimp_filename_to_utf8 (temp_file_name),
                       g_strerror (errno));
          g_unlink (temp_file_name);
          goto err3;
        }

      pp = png_create_write_struct (PNG_LIBPNG_VER_STRING,
                                         NULL, NULL, NULL);
      if (NULL == pp)
        {
          g_warning ("Unable to png_create_write_struct() in mng_save_image()");
          fclose (outfile);
          g_unlink (temp_file_name);
          goto err3;
        }