jpeg.h

/* The GIMP -- an 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 2 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, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

/* JPEG loading and saving file filter for the GIMP
 *  -Peter Mattis
 *
 * This filter is heavily based upon the "example.c" file in libjpeg.
 * In fact most of the loading and saving code was simply cut-and-pasted
 *  from that file. The filter, therefore, also uses libjpeg.
 */

/* 11-JAN-99 - Added support for JPEG comments and Progressive saves.
 *  -pete whiting <pwhiting@sprint.net>
 *
 * Comments of size up to 32k can be stored in the header of jpeg
 * files.  (They are not compressed.)  The JPEG specs and libraries
 * support the storing of multiple comments.  The behavior of this
 * code is to merge all comments in a loading image into a single
 * comment (putting \n between each) and attach that string as a
 * parasite - gimp-comment - to the image.  When saving, the image is
 * checked to see if it has the gimp-comment parasite - if so, that is
 * used as the default comment in the save dialog.  Further, the other
 * jpeg parameters (quality, smoothing, compression and progressive)
 * are attached to the image as a parasite.  This allows the
 * parameters to remain consistent between saves.  I was not able to
 * figure out how to determine the quality, smoothing or compression
 * values of an image as it is being loaded, but the code is there to
 * support it if anyone knows how.  Progressive mode is a method of
 * saving the image such that as a browser (or other app supporting
 * progressive loads - gimp doesn't) loads the image it first gets a
 * low res version displayed and then the image is progressively
 * enhanced until you get the final version.  It doesn't add any size
 * to the image (actually it often results in smaller file size) - the
 * only draw backs are that progressive jpegs are not supported by some
 * older viewers/browsers, and some might find it annoying.
 */

/*
 * 21-AUG-99 - Added support for JPEG previews, subsampling,
 *             non-baseline JPEGs, restart markers and DCT method choice
 * - Steinar H. Gunderson <sgunderson@bigfoot.com>
 *
 * A small preview appears and changes according to the changes to the
 * compression options. The image itself works as a much bigger preview.
 * For slower machines, the save operation (not the load operation) is
 * done in the background, with a standard GTK+ idle loop, which turned
 * out to be the most portable way. Win32 porters shouldn't have much
 * difficulty porting my changes (at least I hope so...).
 *
 * Subsampling is a pretty obscure feature, but I thought it might be nice
 * to have it in anyway, for people to play with :-) Does anybody have
 * any better suggestions than the ones I've put in the menu? (See wizard.doc
 * from the libjpeg distribution for a tiny bit of information on subsampling.)
 *
 * A baseline JPEG is often larger and/or of worse quality than a non-baseline
 * one (especially at low quality settings), but all decoders are guaranteed
 * to read baseline JPEGs (I think). Not all will read a non-baseline one.
 *
 * Restart markers are useful if you are transmitting the image over an
 * unreliable network. If a file gets corrupted, it will only be corrupted
 * up to the next restart marker. Of course, if there are no restart markers,
 * the rest of the image will be corrupted. Restart markers take up extra
 * space. The libjpeg developers recommend a restart every 1 row for
 * transmitting images over unreliable networks, such as Usenet.
 *
 * The DCT method is said by the libjpeg docs to _only_ influence quality vs.
 * speed, and nothing else. However, I've found that there _are_ size
 * differences. Fast integer, on the other hand, is faster than integer,
 * which in turn is faster than FP. According to the libjpeg docs (and I
 * believe it's true), FP has only a theoretical advantage in quality, and
 * will be slower than the two other methods, unless you're blessed with
 * very a fast FPU. (In addition, images might not be identical on
 * different types of FP hardware.)
 *
 * ...and thus ends my additions to the JPEG plug-in. I hope. *sigh* :-)
 */

/*
 * 21-AUG-99 - Bunch O' Fixes.
 * - Adam D. Moss <adam@gimp.org>
 *
 * We now correctly create an alpha-padded layer for our preview --
 * having a non-background non-alpha layer is a no-no in GIMP.
 *
 * I've also tweaked the GIMP undo API a little and changed the JPEG
 * plugin to use gimp_image_{freeze,thaw}_undo so that it doesn't store
 * up a whole load of superfluous tile data every time the preview is
 * changed.
 */

/*
 * 22-DEC-99 - volatiles added
 * - Austin Donnelly <austin@gimp.org>
 *
 * When gcc complains a variable may be clobbered by a longjmp or
 * vfork, it means the following: setjmp() was called by the JPEG
 * library for error recovery purposes, but gcc is keeping some
 * variables in registers without updating the memory locations on the
 * stack consistently.  If JPEG error recovery is every invoked, the
 * values of these variable will be inconsistent.  This is almost
 * always a bug, but not one that's commonly seen unless JPEG recovery
 * code is exercised frequently.  The correct solution is to tell gcc
 * to keep the stack version of the affected variables up to date, by
 * using the "volatile" keyword.   Here endeth the lesson.
 */

/*
 * 4-SEP-01 - remove the use of GtkText
 * - DindinX <David@dindinx.org>
 *
 * The new version of GTK+ does not support GtkText anymore.
 * I've just replaced the one used for the image comment by
 * a GtkTextView/GtkTextBuffer couple;
 */

/*
 * 22-JUN-03 - add support for keeping EXIF information
 * - Dave Neary <bolsh@gimp.org>
 *
 * This is little more than a modified version fo a patch from the
 * libexif owner (Lutz Muller) which attaches exif information to
 * a GimpImage, and if there is infoprmation available at save
 * time, writes it out. No modification of the exif data is
 * currently possible.
 */

#include "config.h"   /* configure cares about HAVE_PROGRESSIVE_JPEG */

#include <glib.h>     /* We want glib.h first because of some
                       * pretty obscure Win32 compilation issues.
                       */
#include <errno.h>
#include <setjmp.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <jpeglib.h>
#include <jerror.h>

#ifdef HAVE_EXIF
#include <libexif/exif-data.h>
#endif /* HAVE_EXIF */

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

#include "libgimp/stdplugins-intl.h"

#define SCALE_WIDTH         125

/* if you are not compiling this from inside the gimp tree, you have to  */
/* take care yourself if your JPEG library supports progressive mode     */
/* #undef HAVE_PROGRESSIVE_JPEG   if your library doesn't support it     */
/* #define HAVE_PROGRESSIVE_JPEG  if your library knows how to handle it */

/* See bugs #63610 and #61088 for a discussion about the quality settings */
#define DEFAULT_QUALITY     85
#define DEFAULT_SMOOTHING   0.0
#define DEFAULT_OPTIMIZE    TRUE
#define DEFAULT_PROGRESSIVE FALSE
#define DEFAULT_BASELINE    TRUE
#define DEFAULT_SUBSMP      0
#define DEFAULT_RESTART     0
#define DEFAULT_DCT         0
#define DEFAULT_PREVIEW     FALSE
#define DEFAULT_EXIF        TRUE

/* sg - these should not be global... */
static gint32 volatile  image_ID_global       = -1;
static gint32           orig_image_ID_global  = -1;
static gint32           drawable_ID_global    = -1;
static gint32           layer_ID_global       = -1;
static GtkWidget       *preview_size          = NULL;
static GimpDrawable    *drawable_global       = NULL;
static gboolean         undo_touched          = FALSE;

typedef struct
{
  gdouble  quality;
  gdouble  smoothing;
  gboolean optimize;
  gboolean progressive;
  gboolean baseline;
  gint     subsmp;
  gint     restart;
  gint     dct;
  gboolean preview;
  gboolean save_exif;
} JpegSaveVals;

typedef struct
{
  struct jpeg_compress_struct cinfo;
  gint          tile_height;
  FILE         *outfile;
  gboolean      has_alpha;
  gint          rowstride;
  guchar       *temp;
  guchar       *data;
  guchar       *src;
  GimpDrawable *drawable;
  GimpPixelRgn  pixel_rgn;
  const gchar  *file_name;
  gboolean      abort_me;
} PreviewPersistent;

static gboolean *abort_me = NULL;


/* 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    load_image          (const gchar      *filename,
                                      GimpRunMode       runmode,
                                      gboolean          preview);
static gboolean  save_image          (const gchar      *filename,
                                      gint32            image_ID,
                                      gint32            drawable_ID,
                                      gint32            orig_image_ID,
                                      gboolean          preview);

static gboolean  save_dialog         (void);

static void      make_preview        (void);
static void      destroy_preview     (void);

static void      save_restart_update (GtkAdjustment    *adjustment,
                                      GtkWidget        *toggle);


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

static JpegSaveVals jsvals =
{
  DEFAULT_QUALITY,
  DEFAULT_SMOOTHING,
  DEFAULT_OPTIMIZE,
  DEFAULT_PROGRESSIVE,
  DEFAULT_BASELINE,
  DEFAULT_SUBSMP,
  DEFAULT_RESTART,
  DEFAULT_DCT,
  DEFAULT_PREVIEW,
  DEFAULT_EXIF
};


static gchar     *image_comment         = NULL;
static GtkWidget *restart_markers_scale = NULL;
static GtkWidget *restart_markers_label = NULL;

#ifdef HAVE_EXIF
static ExifData  *exif_data             = NULL;
#endif /* HAVE_EXIF */

MAIN ()

static void
query (void)
{
  static GimpParamDef load_args[] =
  {
    { GIMP_PDB_INT32,    "run_mode",     "Interactive, non-interactive" },
    { GIMP_PDB_STRING,   "filename",     "The name of the file to load" },
    { GIMP_PDB_STRING,   "raw_filename", "The name of the file to load" }
  };
  static GimpParamDef load_return_vals[] =
  {
    { GIMP_PDB_IMAGE,   "image",         "Output image" }
  };

  static GimpParamDef save_args[] =
  {
    { GIMP_PDB_INT32,    "run_mode",     "Interactive, non-interactive" },
    { GIMP_PDB_IMAGE,    "image",        "Input image" },
    { 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 of the file to save the image in" },
    { GIMP_PDB_FLOAT,    "quality",      "Quality of saved image (0 <= quality <= 1)" },
    { GIMP_PDB_FLOAT,    "smoothing",    "Smoothing factor for saved image (0 <= smoothing <= 1)" },
    { GIMP_PDB_INT32,    "optimize",     "Optimization of entropy encoding parameters (0/1)" },
    { GIMP_PDB_INT32,    "progressive",  "Enable progressive jpeg image loading - ignored if not compiled with HAVE_PROGRESSIVE_JPEG (0/1)" },
    { GIMP_PDB_STRING,   "comment",      "Image comment" },
    { GIMP_PDB_INT32,    "subsmp",       "The subsampling option number" },
    { GIMP_PDB_INT32,    "baseline",     "Force creation of a baseline JPEG (non-baseline JPEGs can't be read by all decoders) (0/1)" },
    { GIMP_PDB_INT32,    "restart",      "Frequency of restart markers (in rows, 0 = no restart markers)" },
    { GIMP_PDB_INT32,    "dct",          "DCT algorithm to use (speed/quality tradeoff)" }
  };

  gimp_install_procedure ("file_jpeg_load",
                          "loads files in the JPEG file format",
                          "loads files in the JPEG file format",
                          "Spencer Kimball, Peter Mattis & others",
                          "Spencer Kimball & Peter Mattis",
                          "1995-1999",
                          N_("JPEG image"),
                          NULL,
                          GIMP_PLUGIN,
                          G_N_ELEMENTS (load_args),
                          G_N_ELEMENTS (load_return_vals),
                          load_args, load_return_vals);

  gimp_plugin_menu_register ("file_jpeg_load", "<Load>");
  gimp_register_file_handler_mime ("file_jpeg_load", "image/jpeg");
  gimp_register_magic_load_handler ("file_jpeg_load",
                                    "jpg,jpeg,jpe",
                                    "",
                                    "6,string,JFIF,6,string,Exif");

  gimp_install_procedure ("file_jpeg_save",
                          "saves files in the JPEG file format",
                          "saves files in the lossy, widely supported JPEG format",
                          "Spencer Kimball, Peter Mattis & others",
                          "Spencer Kimball & Peter Mattis",
                          "1995-1999",
                          N_("JPEG image"),
                          "RGB*, GRAY*",
                          GIMP_PLUGIN,
                          G_N_ELEMENTS (save_args), 0,
                          save_args, NULL);

  gimp_plugin_menu_register ("file_jpeg_save", "<Save>");
  gimp_register_file_handler_mime ("file_jpeg_save", "image/jpeg");
  gimp_register_save_handler ("file_jpeg_save",
                              "jpg,jpeg,jpe",
                              "");
}

static void
run (const gchar      *name,
     gint              nparams,
     const GimpParam  *param,
     gint             *nreturn_vals,
     GimpParam       **return_vals)
{
  static GimpParam   values[2];
  GimpRunMode        run_mode;
  GimpPDBStatusType  status = GIMP_PDB_SUCCESS;
  gint32             image_ID;
  gint32             drawable_ID;
  gint32             orig_image_ID;
  gint32             display_ID = -1;
  GimpParasite      *parasite;
  gboolean           err;
  GimpExportReturn   export = GIMP_EXPORT_CANCEL;

  run_mode = param[0].data.d_int32;

  INIT_I18N ();

  *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_jpeg_load") == 0)
    {
      image_ID = load_image (param[1].data.d_string, run_mode, FALSE);

      if (image_ID != -1)
        {
          *nreturn_vals = 2;
          values[1].type         = GIMP_PDB_IMAGE;
          values[1].data.d_image = image_ID;
        }
      else
        {
          status = GIMP_PDB_EXECUTION_ERROR;
        }
    }
  else if (strcmp (name, "file_jpeg_save") == 0)
    {
      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:
          gimp_ui_init ("jpeg", FALSE);
          export = gimp_export_image (&image_ID, &drawable_ID, "JPEG",
                                      (GIMP_EXPORT_CAN_HANDLE_RGB |
                                       GIMP_EXPORT_CAN_HANDLE_GRAY));
          switch (export)
            {
            case GIMP_EXPORT_EXPORT:
              display_ID = gimp_display_new (image_ID);
              gimp_image_set_filename (image_ID, _("Export Preview"));
              gimp_displays_flush ();
              break;
            case GIMP_EXPORT_IGNORE:
              break;
            case GIMP_EXPORT_CANCEL:
              values[0].data.d_status = GIMP_PDB_CANCEL;
              return;
              break;
            }
          break;
        default:
          break;
        }

#ifdef HAVE_EXIF
      exif_data_unref (exif_data);
      exif_data = NULL;
#endif /* HAVE_EXIF */

      g_free (image_comment);
      image_comment = NULL;

      parasite = gimp_image_parasite_find (orig_image_ID, "gimp-comment");
      if (parasite)
        {
          image_comment = g_strdup (parasite->data);
          gimp_parasite_free (parasite);
        }

#ifdef HAVE_EXIF
      parasite = gimp_image_parasite_find (orig_image_ID, "exif-data");
      if (parasite)
        {
          exif_data = exif_data_new_from_data (parasite->data, parasite->size);
          gimp_parasite_free (parasite);
        }
#endif /* HAVE_EXIF */

      jsvals.quality     = DEFAULT_QUALITY;
      jsvals.smoothing   = DEFAULT_SMOOTHING;
      jsvals.optimize    = DEFAULT_OPTIMIZE;
      jsvals.progressive = DEFAULT_PROGRESSIVE;
      jsvals.baseline    = DEFAULT_BASELINE;
      jsvals.subsmp      = DEFAULT_SUBSMP;
      jsvals.restart     = DEFAULT_RESTART;
      jsvals.dct         = DEFAULT_DCT;
      jsvals.preview     = DEFAULT_PREVIEW;
      jsvals.save_exif   = DEFAULT_EXIF;

      switch (run_mode)
        {
        case GIMP_RUN_INTERACTIVE:
          /*  Possibly retrieve data  */
          gimp_get_data ("file_jpeg_save", &jsvals);

          /* load up the previously used values */
          parasite = gimp_image_parasite_find (orig_image_ID,
                                               "jpeg-save-options");
          if (parasite)
            {
              jsvals.quality     = ((JpegSaveVals *)parasite->data)->quality;
              jsvals.smoothing   = ((JpegSaveVals *)parasite->data)->smoothing;
              jsvals.optimize    = ((JpegSaveVals *)parasite->data)->optimize;
              jsvals.progressive = ((JpegSaveVals *)parasite->data)->progressive;
              jsvals.baseline    = ((JpegSaveVals *)parasite->data)->baseline;
              jsvals.subsmp      = ((JpegSaveVals *)parasite->data)->subsmp;
              jsvals.restart     = ((JpegSaveVals *)parasite->data)->restart;
              jsvals.dct         = ((JpegSaveVals *)parasite->data)->dct;
              jsvals.preview     = ((JpegSaveVals *)parasite->data)->preview;
              jsvals.save_exif   = ((JpegSaveVals *)parasite->data)->save_exif;
              gimp_parasite_free (parasite);
            }

          if (jsvals.preview)
            {
              /* we freeze undo saving so that we can avoid sucking up
               * tile cache with our unneeded preview steps. */
              gimp_image_undo_freeze (image_ID);

              undo_touched = TRUE;
            }

          /* prepare for the preview */
          image_ID_global = image_ID;
          orig_image_ID_global = orig_image_ID;
          drawable_ID_global = drawable_ID;

          /*  First acquire information with a dialog  */
          err = save_dialog ();

          if (undo_touched)
            {
              /* thaw undo saving and flush the displays to have them
               * reflect the current shortcuts */
              gimp_image_undo_thaw (image_ID);
              gimp_displays_flush ();
            }

          if (!err)
            status = GIMP_PDB_CANCEL;
          break;

        case GIMP_RUN_NONINTERACTIVE:
          /*  Make sure all the arguments are there!  */
          /*  pw - added two more progressive and comment */
          /*  sg - added subsampling, preview, baseline, restarts and DCT */
          if (nparams != 14)
            {
              status = GIMP_PDB_CALLING_ERROR;
            }
          else
            {
              /* Once the PDB gets default parameters, remove this hack */
              if (param[5].data.d_float > 0.05)
                {
                  jsvals.quality     = 100.0 * param[5].data.d_float;
                  jsvals.smoothing   = param[6].data.d_float;
                  jsvals.optimize    = param[7].data.d_int32;
#ifdef HAVE_PROGRESSIVE_JPEG
                  jsvals.progressive = param[8].data.d_int32;
#endif /* HAVE_PROGRESSIVE_JPEG */
                  jsvals.baseline    = param[11].data.d_int32;
                  jsvals.subsmp      = param[10].data.d_int32;
                  jsvals.restart     = param[12].data.d_int32;
                  jsvals.dct         = param[13].data.d_int32;

                  /* free up the default -- wasted some effort earlier */
                  g_free (image_comment);
                  image_comment = g_strdup (param[9].data.d_string);
                }

              jsvals.preview = FALSE;

              if (jsvals.quality < 0.0 || jsvals.quality > 100.0)
                status = GIMP_PDB_CALLING_ERROR;
              else if (jsvals.smoothing < 0.0 || jsvals.smoothing > 1.0)
                status = GIMP_PDB_CALLING_ERROR;
              else if (jsvals.subsmp < 0 || jsvals.subsmp > 2)
                status = GIMP_PDB_CALLING_ERROR;
              else if (jsvals.dct < 0 || jsvals.dct > 2)
                status = GIMP_PDB_CALLING_ERROR;
            }
          break;

        case GIMP_RUN_WITH_LAST_VALS:
          /*  Possibly retrieve data  */
          gimp_get_data ("file_jpeg_save", &jsvals);

          parasite = gimp_image_parasite_find (orig_image_ID,
                                               "jpeg-save-options");
          if (parasite)
            {
              jsvals.quality     = ((JpegSaveVals *)parasite->data)->quality;
              jsvals.smoothing   = ((JpegSaveVals *)parasite->data)->smoothing;
              jsvals.optimize    = ((JpegSaveVals *)parasite->data)->optimize;
              jsvals.progressive = ((JpegSaveVals *)parasite->data)->progressive;
              jsvals.baseline    = ((JpegSaveVals *)parasite->data)->baseline;
              jsvals.subsmp      = ((JpegSaveVals *)parasite->data)->subsmp;
              jsvals.restart     = ((JpegSaveVals *)parasite->data)->restart;
              jsvals.dct         = ((JpegSaveVals *)parasite->data)->dct;
              jsvals.preview     = FALSE;
              gimp_parasite_free (parasite);
            }
          break;

        default:
          break;
        }

      if (status == GIMP_PDB_SUCCESS)
        {
          if (save_image (param[3].data.d_string,
                          image_ID,
                          drawable_ID,
                          orig_image_ID,
                          FALSE))
            {
              /*  Store mvals data  */
              gimp_set_data ("file_jpeg_save", &jsvals, sizeof (JpegSaveVals));
            }
          else
            {
              status = GIMP_PDB_EXECUTION_ERROR;
            }
        }

      if (export == GIMP_EXPORT_EXPORT)
        {
          /* If the image was exported, delete the new display. */
          /* This also deletes the image.                       */

          if (display_ID > -1)
            gimp_display_delete (display_ID);
          else
            gimp_image_delete (image_ID);
        }

      /* pw - now we need to change the defaults to be whatever
       * was used to save this image.  Dump the old parasites
       * and add new ones. */

      gimp_image_parasite_detach (orig_image_ID, "gimp-comment");
      if (image_comment && strlen (image_comment))
        {
          parasite = gimp_parasite_new ("gimp-comment",
                                        GIMP_PARASITE_PERSISTENT,
                                        strlen (image_comment) + 1,
                                        image_comment);
          gimp_image_parasite_attach (orig_image_ID, parasite);
          gimp_parasite_free (parasite);
        }
      gimp_image_parasite_detach (orig_image_ID, "jpeg-save-options");

      parasite = gimp_parasite_new ("jpeg-save-options",
                                    0, sizeof (jsvals), &jsvals);
      gimp_image_parasite_attach (orig_image_ID, parasite);
      gimp_parasite_free (parasite);
    }
  else
    {
      status = GIMP_PDB_CALLING_ERROR;
    }

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

/* Read next byte */
static guint
jpeg_getc (j_decompress_ptr cinfo)
{
  struct jpeg_source_mgr *datasrc = cinfo->src;

  if (datasrc->bytes_in_buffer == 0)
    {
      if (! (*datasrc->fill_input_buffer) (cinfo))
        ERREXIT (cinfo, JERR_CANT_SUSPEND);
    }
  datasrc->bytes_in_buffer--;

  return *datasrc->next_input_byte++;
}

/* We need our own marker parser, since early versions of libjpeg
 * don't keep a conventient list of the marker's that have been
 * seen. */

/*
 * Marker processor for COM markers.
 * This replaces the library's built-in processor, which just skips the marker.
 * Note this code relies on a non-suspending data source.
 */
static GString *local_image_comments = NULL;

static boolean
COM_handler (j_decompress_ptr cinfo)
{
  gint  length;
  guint ch;

  length = jpeg_getc (cinfo) << 8;
  length += jpeg_getc (cinfo);
  if (length < 2)
    return FALSE;
  length -= 2;                  /* discount the length word itself */

  if (!local_image_comments)
    local_image_comments = g_string_new (NULL);
  else
    g_string_append_c (local_image_comments, '\n');

  while (length-- > 0)
    {
      ch = jpeg_getc (cinfo);
      g_string_append_c (local_image_comments, ch);
    }

  return TRUE;
}

typedef struct my_error_mgr
{
  struct jpeg_error_mgr pub;            /* "public" fields */

#ifdef __ia64__
  /* Ugh, the jmp_buf field needs to be 16-byte aligned on ia64 and some
   * glibc/icc combinations don't guarantee this. So we pad. See bug #138357
   * for details.
   */
  long double           dummy;
#endif

  jmp_buf               setjmp_buffer;  /* for return to caller */
} *my_error_ptr;

/*
 * Here's the routine that will replace the standard error_exit method:
 */

static void
my_error_exit (j_common_ptr cinfo)
{
  /* cinfo->err really points to a my_error_mgr struct, so coerce pointer */
  my_error_ptr myerr = (my_error_ptr) cinfo->err;

  /* Always display the message. */
  /* We could postpone this until after returning, if we chose. */
  (*cinfo->err->output_message) (cinfo);

  /* Return control to the setjmp point */
  longjmp (myerr->setjmp_buffer, 1);
}

static void
my_emit_message (j_common_ptr cinfo,
                 int          msg_level)
{
  if (msg_level == -1)
    {
      /*  disable loading of EXIF data  */
      cinfo->client_data = GINT_TO_POINTER (TRUE);

      (*cinfo->err->output_message) (cinfo);
    }
}

static void
my_output_message (j_common_ptr cinfo)
{
  gchar  buffer[JMSG_LENGTH_MAX + 1];

  (*cinfo->err->format_message)(cinfo, buffer);

  if (GPOINTER_TO_INT (cinfo->client_data))
    {
      gchar *msg = g_strconcat (buffer,
                                "\n\n",
                                _("EXIF data will be ignored."),
                                NULL);
      g_message (msg);
      g_free (msg);
    }
  else
    {
      g_message (buffer);
    }
}

static gint32
load_image (const gchar *filename,
            GimpRunMode  runmode,
            gboolean     preview)
{
  GimpPixelRgn     pixel_rgn;
  GimpDrawable    *drawable;
  gint32 volatile  image_ID;
  gint32           layer_ID;
  struct jpeg_decompress_struct cinfo;
  struct my_error_mgr           jerr;
  FILE    *infile;
  guchar  *buf;
  guchar  * volatile padded_buf = NULL;
  guchar **rowbuf;
  gint     image_type;
  gint     layer_type;
  gint     tile_height;
  gint     scanlines;
  gint     i, start, end;

  GimpParasite * volatile comment_parasite = NULL;

#ifdef HAVE_EXIF
  GimpParasite *exif_parasite = NULL;
  ExifData     *exif_data     = NULL;
#endif

  /* We set up the normal JPEG error routines. */
  cinfo.err = jpeg_std_error (&jerr.pub);
  jerr.pub.error_exit = my_error_exit;

  /* flag warnings, so we try to ignore corrupt EXIF data */
  if (!preview)
    {
      cinfo.client_data = GINT_TO_POINTER (FALSE);

      jerr.pub.emit_message   = my_emit_message;
      jerr.pub.output_message = my_output_message;
    }

  if ((infile = fopen (filename, "rb")) == NULL)
    {
      g_message (_("Could not open '%s' for reading: %s"),
                 gimp_filename_to_utf8 (filename), g_strerror (errno));
      gimp_quit ();
    }

  if (!preview)
    {
      gchar *name = g_strdup_printf (_("Opening '%s'..."),
                                     gimp_filename_to_utf8 (filename));

      gimp_progress_init (name);
      g_free (name);
    }

  image_ID = -1;
  /* Establish the setjmp return context for my_error_exit to use. */
  if (setjmp (jerr.setjmp_buffer))
    {
      /* If we get here, the JPEG code has signaled an error.
       * We need to clean up the JPEG object, close the input file, and return.
       */
      jpeg_destroy_decompress (&cinfo);
      if (infile)
        fclose (infile);
      if (image_ID != -1 && !preview)
        gimp_image_delete (image_ID);
      if (preview)
        destroy_preview();
      gimp_quit ();
    }

  /* Now we can initialize the JPEG decompression object. */
  jpeg_create_decompress (&cinfo);

  /* Step 2: specify data source (eg, a file) */

  jpeg_stdio_src (&cinfo, infile);

  /* pw - step 2.1 let the lib know we want the comments. */

  jpeg_set_marker_processor (&cinfo, JPEG_COM, COM_handler);

  /* Step 3: read file parameters with jpeg_read_header() */

  (void) jpeg_read_header (&cinfo, TRUE);

  /* We can ignore the return value from jpeg_read_header since
   *   (a) suspension is not possible with the stdio data source, and
   *   (b) we passed TRUE to reject a tables-only JPEG file as an error.
   * See libjpeg.doc for more info.
   */

  if (!preview)
    {
      /* if we had any comments then make a parasite for them */
      if (local_image_comments && local_image_comments->len)
        {
          gchar *comment = local_image_comments->str;

          g_string_free (local_image_comments, FALSE);

          local_image_comments = NULL;

          if (g_utf8_validate (comment, -1, NULL))
            comment_parasite = gimp_parasite_new ("gimp-comment",
                                                  GIMP_PARASITE_PERSISTENT,
                                                  strlen (comment) + 1,
                                                  comment);
          g_free (comment);
        }

      /* Do not attach the "jpeg-save-options" parasite to the image
       * because this conflics with the global defaults.  See bug #75398:
       * http://bugzilla.gnome.org/show_bug.cgi?id=75398 */
    }

  /* Step 4: set parameters for decompression */

  /* In this example, we don't need to change any of the defaults set by
   * jpeg_read_header(), so we do nothing here.
   */

  /* Step 5: Start decompressor */

  jpeg_start_decompress (&cinfo);

  /* We may need to do some setup of our own at this point before reading
   * the data.  After jpeg_start_decompress() we have the correct scaled
   * output image dimensions available, as well as the output colormap
   * if we asked for color quantization.
   * In this example, we need to make an output work buffer of the right size.
   */
  /* temporary buffer */
  tile_height = gimp_tile_height ();
  buf = g_new (guchar,
               tile_height * cinfo.output_width * cinfo.output_components);

  rowbuf = g_new (guchar*, tile_height);

  for (i = 0; i < tile_height; i++)
    rowbuf[i] = buf + cinfo.output_width * cinfo.output_components * i;

  /* Create a new image of the proper size and associate the filename with it.

     Preview layers, not being on the bottom of a layer stack, MUST HAVE
     AN ALPHA CHANNEL!
   */
  switch (cinfo.output_components)
    {
    case 1:
      image_type = GIMP_GRAY;
      layer_type = preview ? GIMP_GRAYA_IMAGE : GIMP_GRAY_IMAGE;
      break;

    case 3:
      image_type = GIMP_RGB;
      layer_type = preview ? GIMP_RGBA_IMAGE : GIMP_RGB_IMAGE;
      break;

    case 4:
      if (cinfo.out_color_space == JCS_CMYK)
        {
          image_type = GIMP_RGB;
          layer_type = GIMP_RGB_IMAGE;
          break;
        }
      /*fallthrough*/

    default:
      g_message ("Don't know how to load JPEGs\n"
                 "with %d color channels\n"
                 "using colorspace %d (%d)",
                 cinfo.output_components, cinfo.out_color_space,
                 cinfo.jpeg_color_space);
      gimp_quit ();
      break;
    }

  if (preview)
    padded_buf = g_new (guchar, tile_height * cinfo.output_width *
                        (cinfo.output_components + 1));
  else if (cinfo.out_color_space == JCS_CMYK)
    padded_buf = g_new (guchar, tile_height * cinfo.output_width * 3);
  else
    padded_buf = NULL;

  if (preview)
    {
      image_ID = image_ID_global;
    }
  else
    {
      image_ID = gimp_image_new (cinfo.output_width, cinfo.output_height,
                                 image_type);
      gimp_image_set_filename (image_ID, filename);
    }

  if (preview)
    {
      layer_ID_global = layer_ID =
        gimp_layer_new (image_ID, _("JPEG preview"),
                        cinfo.output_width,
                        cinfo.output_height,
                        layer_type, 100, GIMP_NORMAL_MODE);
    }
  else
    {
      layer_ID = gimp_layer_new (image_ID, _("Background"),
                                 cinfo.output_width,
                                 cinfo.output_height,
                                 layer_type, 100, GIMP_NORMAL_MODE);
    }

  drawable_global = drawable = gimp_drawable_get (layer_ID);
  gimp_pixel_rgn_init (&pixel_rgn, drawable, 0, 0,
                       drawable->width, drawable->height, TRUE, FALSE);

  /* Step 5.1: if the file had resolution information, set it on the image */
  if (!preview && cinfo.saw_JFIF_marker)
    {
      gdouble xresolution;
      gdouble yresolution;
      gdouble asymmetry;

      xresolution = cinfo.X_density;
      yresolution = cinfo.Y_density;

      switch (cinfo.density_unit)
        {