jpeg-load.c 58.9 KB
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/* 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
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 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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 */

/* 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.
 */

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/* 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 (quaility, 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 quaility, 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
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 * 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.
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 */

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/* 
 * 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* :-)
 */

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/* 
 * 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.
 */

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/*
 * 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.
 */


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#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.
				 */
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#include <setjmp.h>
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#include <signal.h>
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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#ifdef HAVE_UNISTD_H
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#include <unistd.h>
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#endif
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#include <jpeglib.h>
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#include <jerror.h>
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#include <libgimp/gimp.h>
#include <libgimp/gimpui.h>
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#include "libgimp/stdplugins-intl.h"

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#define SCALE_WIDTH         125
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/* if you are not compiling this from inside the gimp tree, you have to  */
/* take care yourself if your JPEG library supports progressive mode     */
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/* #undef HAVE_PROGRESSIVE_JPEG   if your library doesn't support it     */
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/* #define HAVE_PROGRESSIVE_JPEG  if your library knows how to handle it */

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#define DEFAULT_QUALITY     0.75
#define DEFAULT_SMOOTHING   0.0
#define DEFAULT_OPTIMIZE    1
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#define DEFAULT_PROGRESSIVE 0
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#define DEFAULT_BASELINE    1
#define DEFAULT_SUBSMP      0
#define DEFAULT_RESTART     0
#define DEFAULT_DCT         0
#define DEFAULT_PREVIEW     1
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#define DEFAULT_COMMENT     "Created with The GIMP"
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/* sg - these should not be global... */
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static gint32 volatile  image_ID_global = -1;
static gint32           orig_image_ID_global;
static gint32           drawable_ID_global = -1;
static gint32           layer_ID_global = -1;
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static GtkWidget       *preview_size = NULL;
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static GimpDrawable       *drawable_global = NULL;
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typedef struct
{
  gdouble quality;
  gdouble smoothing;
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  gint    optimize;
  gint    progressive;
  gint    baseline;
  gint    subsmp;
  gint    restart;
  gint    dct;
  gint    preview;
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} JpegSaveVals;

typedef struct
{
  gint  run;
} JpegSaveInterface;

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

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/* Declare local functions.
 */
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static void   query                     (void);
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static void   run                       (gchar         *name,
					 gint           nparams,
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					 GimpParam        *param,
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					 gint          *nreturn_vals,
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					 GimpParam       **return_vals);
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static gint32 load_image                (gchar         *filename, 
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					 GimpRunModeType   runmode, 
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					 gint           preview);
static gint   save_image                (gchar         *filename,
					 gint32         image_ID,
					 gint32         drawable_ID,
					 gint32         orig_image_ID,
					 gint           preview);
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static void   add_menu_item             (GtkWidget *menu,
					 char *label,
					 guint op_no,
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					 GtkSignalFunc callback);
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static gint   save_dialog                (void);

static void   save_close_callback        (GtkWidget *widget,
					  gpointer   data);
static void   save_ok_callback           (GtkWidget *widget,
					  gpointer   data);
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static void   save_restart_toggle_update (GtkWidget     *toggle,
					  GtkAdjustment *adjustment);
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static void   save_restart_update        (GtkAdjustment *adjustment,
					  GtkWidget     *toggle);

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

static void   subsmp_callback            (GtkWidget *widget, 
					  gpointer data);
static void   dct_callback               (GtkWidget *widget, 
					  gpointer data);
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GimpPlugInInfo PLUG_IN_INFO =
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{
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  NULL,  /* init_proc  */
  NULL,  /* quit_proc  */
  query, /* query_proc */
  run,   /* run_proc   */
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};

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

static JpegSaveInterface jsint =
{
  FALSE   /*  run  */
};

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

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MAIN ()

static void
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query (void)
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{
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  static GimpParamDef load_args[] =
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  {
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    { 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" }
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  };
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  static GimpParamDef load_return_vals[] =
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  {
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    { GIMP_PDB_IMAGE,   "image",         "Output image" }
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  };
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  static gint nload_args        = sizeof (load_args) / sizeof (load_args[0]);
  static gint nload_return_vals = (sizeof (load_return_vals) /
				   sizeof (load_return_vals[0]));
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  static GimpParamDef save_args[] =
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  {
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    { 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)" }
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  };
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  static gint nsave_args = sizeof (save_args) / sizeof (save_args[0]);
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  gimp_install_procedure ("file_jpeg_load",
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                          "loads files in the JPEG file format",
                          "loads files in the JPEG file format",
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                          "Spencer Kimball, Peter Mattis & others",
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                          "Spencer Kimball & Peter Mattis",
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                          "1995-1999",
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			  "<Load>/Jpeg",
			  NULL,
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                          GIMP_PLUGIN,
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                          nload_args, nload_return_vals,
                          load_args, load_return_vals);

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

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  gimp_register_magic_load_handler ("file_jpeg_load",
				    "jpg,jpeg",
				    "",
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				    "6,string,JFIF,6,string,Exif");
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  gimp_register_save_handler       ("file_jpeg_save",
				    "jpg,jpeg",
				    "");
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}

static void
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run (gchar   *name,
     gint     nparams,
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     GimpParam  *param,
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     gint    *nreturn_vals,
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     GimpParam **return_vals)
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{
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  static GimpParam values[2];
  GimpRunModeType  run_mode;
  GimpPDBStatusType   status = GIMP_PDB_SUCCESS;
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  gint32        image_ID;
  gint32        drawable_ID;
  gint32        orig_image_ID;
  gint32        display_ID = -1;
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#ifdef GIMP_HAVE_PARASITES
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  GimpParasite *parasite;
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#endif /* GIMP_HAVE_PARASITES */
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  gint          err;
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  GimpExportReturnType export = EXPORT_CANCEL;
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  run_mode = param[0].data.d_int32;

  *nreturn_vals = 1;
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  *return_vals  = values;
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  values[0].type          = GIMP_PDB_STATUS;
  values[0].data.d_status = GIMP_PDB_EXECUTION_ERROR;
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  if (strcmp (name, "file_jpeg_load") == 0)
    {
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      INIT_I18N();

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      image_ID = load_image (param[1].data.d_string, run_mode, FALSE);
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      if (image_ID != -1)
	{
	  *nreturn_vals = 2;
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	  values[1].type         = GIMP_PDB_IMAGE;
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	  values[1].data.d_image = image_ID;
	}
      else
	{
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	  status = GIMP_PDB_EXECUTION_ERROR;
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	}
    }
  else if (strcmp (name, "file_jpeg_save") == 0)
    {
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      INIT_I18N_UI();
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      image_ID = orig_image_ID = param[1].data.d_int32;
      drawable_ID = param[2].data.d_int32;

       /*  eventually export the image */ 
      switch (run_mode)
	{
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	case GIMP_RUN_INTERACTIVE:
	case GIMP_RUN_WITH_LAST_VALS:
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	  gimp_ui_init ("jpeg", FALSE);
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	  export = gimp_export_image (&image_ID, &drawable_ID, "JPEG", 
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				      (CAN_HANDLE_RGB |
				       CAN_HANDLE_GRAY));
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	  switch (export)
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	    {
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	    case EXPORT_EXPORT: 
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	      display_ID = gimp_display_new (image_ID);
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	      gimp_image_set_filename (image_ID, _("Export Preview"));
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	      gimp_displays_flush ();
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	      break;
	    case EXPORT_IGNORE:
	      break;
	    case EXPORT_CANCEL:
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	      values[0].data.d_status = GIMP_PDB_CANCEL;
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	      return;
	      break;
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	    }
	  break;
	default:
	  break;
	}
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      if (image_comment) 
	{
	  g_free (image_comment);
	  image_comment = NULL;
	}
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#ifdef GIMP_HAVE_PARASITES
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      parasite = gimp_image_parasite_find (orig_image_ID, "gimp-comment");
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      if (parasite) 
	{
	  image_comment = g_strdup (parasite->data);
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	  gimp_parasite_free (parasite);
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	}
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#endif /* GIMP_HAVE_PARASITES */
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      if (!image_comment) 
	image_comment = g_strdup (DEFAULT_COMMENT);

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

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

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#ifdef GIMP_HAVE_PARASITES
	  /* load up the previously used values */
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	  parasite = gimp_image_parasite_find (orig_image_ID,
					       "jpeg-save-options");
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	  if (parasite)
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	    {
	      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;
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	      gimp_parasite_free (parasite);
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	    }
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#endif /* GIMP_HAVE_PARASITES */
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	  /* we start an undo_group and immediately freeze undo saving
	     so that we can avoid sucking up tile cache with our unneeded
	     preview steps. */
      	  gimp_undo_push_group_start (image_ID);
      	  gimp_image_undo_freeze (image_ID);

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	  /* prepare for the preview */
	  image_ID_global = image_ID;
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	  orig_image_ID_global = orig_image_ID;
	  drawable_ID_global = drawable_ID;
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	  /*  First acquire information with a dialog  */
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	  err = save_dialog ();
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	  /* thaw undo saving and end the undo_group. */
	  gimp_image_undo_thaw (image_ID);
	  gimp_undo_push_group_end (image_ID); 
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          if (!err)
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	    status = GIMP_PDB_CANCEL;
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	  break;

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	case GIMP_RUN_NONINTERACTIVE:
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	  /*  Make sure all the arguments are there!  */
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	  /*  pw - added two more progressive and comment */
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	  /*  sg - added subsampling, preview, baseline, restarts and DCT */
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	  if (nparams != 14)
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	    {
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	      status = GIMP_PDB_CALLING_ERROR;
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	    }
	  else
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	    {
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	      jsvals.quality     = param[5].data.d_float;
	      jsvals.smoothing   = param[6].data.d_float;
	      jsvals.optimize    = param[7].data.d_int32;
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#ifdef HAVE_PROGRESSIVE_JPEG
	      jsvals.progressive = param[8].data.d_int32;
#endif /* HAVE_PROGRESSIVE_JPEG */
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	      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;
	      jsvals.preview     = FALSE;
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	      /* free up the default -- wasted some effort earlier */
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	      if (image_comment) 
		g_free (image_comment);
	      image_comment = g_strdup (param[9].data.d_string);
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	      if (jsvals.quality < 0.0 || jsvals.quality > 1.0)
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		status = GIMP_PDB_CALLING_ERROR;
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	      else if (jsvals.smoothing < 0.0 || jsvals.smoothing > 1.0)
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		status = GIMP_PDB_CALLING_ERROR;
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	      else if (jsvals.subsmp < 0 || jsvals.subsmp > 2)
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		status = GIMP_PDB_CALLING_ERROR;
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	      else if (jsvals.dct < 0 || jsvals.dct > 2)
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		status = GIMP_PDB_CALLING_ERROR;
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	    }
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	  break;
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	case GIMP_RUN_WITH_LAST_VALS:
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	  /*  Possibly retrieve data  */
	  gimp_get_data ("file_jpeg_save", &jsvals);
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#ifdef GIMP_HAVE_PARASITES
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	  parasite = gimp_image_parasite_find (orig_image_ID,
					       "jpeg-save-options");
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	  if (parasite)
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	    {
	      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;
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	      gimp_parasite_free (parasite);
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	    }
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#endif /* GIMP_HAVE_PARASITES */
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	  break;

	default:
	  break;
	}

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      if (status == GIMP_PDB_SUCCESS)
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	{
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	  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
	    {
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	      status = GIMP_PDB_EXECUTION_ERROR;
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	    }
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	}
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      if (export == EXPORT_EXPORT)
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	{
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	  /* If the image was exported, delete the new display. */
	  /* This also deletes the image.                       */
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	  if (display_ID > -1)
	    gimp_display_delete (display_ID);
	  else
	    gimp_image_delete (image_ID);
	}

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#ifdef GIMP_HAVE_PARASITES
      /* 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. */
      
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      gimp_image_parasite_detach (orig_image_ID, "gimp-comment");
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      if (strlen (image_comment)) 
	{
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	  parasite = gimp_parasite_new ("gimp-comment",
					GIMP_PARASITE_PERSISTENT,
					strlen (image_comment) + 1,
					image_comment);
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	  gimp_image_parasite_attach (orig_image_ID, parasite);
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	  gimp_parasite_free (parasite);
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	}
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      gimp_image_parasite_detach (orig_image_ID, "jpeg-save-options");
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      parasite = gimp_parasite_new ("jpeg-save-options",
				    0, sizeof (jsvals), &jsvals);
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      gimp_image_parasite_attach (orig_image_ID, parasite);
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      gimp_parasite_free (parasite);
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#endif /* Have Parasites */  
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    }
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  else
    {
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      status = GIMP_PDB_CALLING_ERROR;
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    }
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  values[0].data.d_status = status;
}
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/* Read next byte */
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static guint
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jpeg_getc (j_decompress_ptr cinfo)
{
  struct jpeg_source_mgr * datasrc = cinfo->src;

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  if (datasrc->bytes_in_buffer == 0) 
    {
      if (! (*datasrc->fill_input_buffer) (cinfo))
	ERREXIT (cinfo, JERR_CANT_SUSPEND);
    }
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  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.
 */
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static GString *local_image_comments = NULL;
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static boolean
COM_handler (j_decompress_ptr cinfo)
{
  int length;
  unsigned int 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)
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    {
      ch = jpeg_getc (cinfo);
      g_string_append_c (local_image_comments, ch);
    }
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  return TRUE;
}

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typedef struct my_error_mgr
{
  struct jpeg_error_mgr pub;            /* "public" fields */
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  jmp_buf               setjmp_buffer;  /* for return to caller */
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} *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 gint32
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load_image (gchar        *filename, 
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	    GimpRunModeType  runmode, 
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	    gint          preview)
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{
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  GimpPixelRgn pixel_rgn;
  GimpDrawable *drawable;
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  gint32 volatile image_ID;
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  gint32 layer_ID;
  struct jpeg_decompress_struct cinfo;
  struct my_error_mgr jerr;
  FILE *infile;
  guchar *buf;
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  guchar * volatile padded_buf = NULL;
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  guchar **rowbuf;
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  gchar *name;
  gint image_type;
  gint layer_type;
  gint tile_height;
  gint scanlines;
  gint i, start, end;
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#ifdef GIMP_HAVE_PARASITES
  JpegSaveVals local_save_vals;
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  GimpParasite * volatile comment_parasite = NULL;
  GimpParasite * volatile vals_parasite = NULL;
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#endif /* GIMP_HAVE_PARASITES */
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  /* We set up the normal JPEG error routines. */
  cinfo.err = jpeg_std_error (&jerr.pub);
  jerr.pub.error_exit = my_error_exit;

  if ((infile = fopen (filename, "rb")) == NULL)
    {
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      g_warning (_("can't open \"%s\"\n"), filename);
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      gimp_quit ();
    }

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  if (runmode != GIMP_RUN_NONINTERACTIVE)
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    {
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      name = g_strdup_printf (_("Loading %s:"), filename);
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      gimp_progress_init (name);
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      g_free (name);
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    }
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  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);
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      if (image_ID != -1 && !preview)
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	gimp_image_delete (image_ID);
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      if (preview)
	destroy_preview();
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      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);

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  /* pw - step 2.1 let the lib know we want the comments. */
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  jpeg_set_marker_processor (&cinfo, JPEG_COM, COM_handler);
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  /* 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.
   */

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#ifdef GIMP_HAVE_PARASITES
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  if (!preview) {
    /* if we had any comments then make a parasite for them */
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    if (local_image_comments) 
      {
	char *string = local_image_comments->str;
	g_string_free (local_image_comments,FALSE);
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	local_image_comments = NULL;
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	comment_parasite = gimp_parasite_new ("gimp-comment",
					      GIMP_PARASITE_PERSISTENT,
					      strlen (string) + 1, string);
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      } 
    else 
      {
	comment_parasite = NULL;
      }
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    /* pw - figuring out what the saved values were is non-trivial.
     * They don't seem to be in the cinfo structure. For now, I will
     * just use the defaults, but if someone figures out how to derive
     * them this is the place to store them. */

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    local_save_vals.quality     = DEFAULT_QUALITY;
    local_save_vals.smoothing   = DEFAULT_SMOOTHING;
    local_save_vals.optimize    = DEFAULT_OPTIMIZE;
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#ifdef HAVE_PROGRESSIVE_JPEG 
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    local_save_vals.progressive = cinfo.progressive_mode;
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#else
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    local_save_vals.progressive = 0;
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#endif /* HAVE_PROGRESSIVE_JPEG */
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    local_save_vals.baseline    = DEFAULT_BASELINE;
    local_save_vals.subsmp      = DEFAULT_SUBSMP;   /* sg - this _is_ there, but I'm too lazy */ 
    local_save_vals.restart     = DEFAULT_RESTART;
    local_save_vals.dct         = DEFAULT_DCT;
    local_save_vals.preview     = DEFAULT_PREVIEW;
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    vals_parasite = gimp_parasite_new ("jpeg-save-options", 0,
				       sizeof (local_save_vals),
				       &local_save_vals);
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  } 
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#endif /* GIMP_HAVE_PARASITES */
  
  
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  /* 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);
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  if (preview)
    padded_buf = g_new (guchar, tile_height * cinfo.output_width *
			(cinfo.output_components + 1));

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  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.
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     Preview layers, not being on the bottom of a layer stack, MUST HAVE
     AN ALPHA CHANNEL!
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   */
  switch (cinfo.output_components)
    {
    case 1:
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      image_type = GIMP_GRAY;
      layer_type = preview ? GIMP_GRAYA_IMAGE : GIMP_GRAY_IMAGE;
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      break;
    case 3:
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      image_type = GIMP_RGB;
      layer_type = preview ? GIMP_RGBA_IMAGE : GIMP_RGB_IMAGE;
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      break;
    default:
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      g_message ("don't know how to load JPEGs\nwith %d color channels",
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                   cinfo.output_components);
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      gimp_quit ();
    }

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  if (preview) 
    {
      image_ID = image_ID_global;
    } 
  else 
    {
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      image_ID = gimp_image_new (cinfo.output_width, cinfo.output_height,
				 image_type);
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      gimp_image_set_filename (image_ID, filename);
    }
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  if (preview) 
    {
      layer_ID_global = layer_ID = gimp_layer_new (image_ID, _("JPEG preview"),
						   cinfo.output_width,
						   cinfo.output_height,
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						   layer_type, 100, GIMP_NORMAL_MODE);
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    }
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  else 
    {
      layer_ID = gimp_layer_new (image_ID, _("Background"),
				 cinfo.output_width,
				 cinfo.output_height,
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				 layer_type, 100, GIMP_NORMAL_MODE);
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    }
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  drawable_global = drawable = gimp_drawable_get (layer_ID);
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  gimp_pixel_rgn_init (&pixel_rgn, drawable, 0, 0,
		       drawable->width, drawable->height, TRUE, FALSE);
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#ifdef GIMP_HAVE_RESOLUTION_INFO
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  /* Step 5.1: if the file had resolution information, set it on the image */
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  if (!preview && cinfo.saw_JFIF_marker)
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    {
      gdouble xresolution;
      gdouble yresolution;
      gdouble asymmetry;
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      xresolution = cinfo.X_density;
      yresolution = cinfo.Y_density;
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      switch (cinfo.density_unit)
	{
	case 0: /* unknown -> set the aspect ratio but use the default
		*  image resolution
		*/
	  asymmetry = xresolution / yresolution;
	  gimp_image_get_resolution (image_ID, &xresolution, &yresolution);
	  xresolution *= asymmetry;
	  break;
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	case 1: /* dots per inch */
	  break;
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	case 2: /* dots per cm */
	  xresolution *= 2.54;
	  yresolution *= 2.54;
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	  gimp_image_set_unit (image_ID, GIMP_UNIT_MM);
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	  break;

	default:
	  g_message ("unknown density unit %d\nassuming dots per inch",
		     cinfo.density_unit);
	  break;
	}

      gimp_image_set_resolution (image_ID, xresolution, yresolution);
    }
#endif /* GIMP_HAVE_RESOLUTION_INFO */
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  /* Step 6: while (scan lines remain to be read) */
  /*           jpeg_read_scanlines(...); */

  /* Here we use the library's state variable cinfo.output_scanline as the
   * loop counter, so that we don't have to keep track ourselves.
   */
  while (cinfo.output_scanline < cinfo.output_height)
    {
      start = cinfo.output_scanline;
      end = cinfo.output_scanline + tile_height;
      end = MIN (end, cinfo.output_height);
      scanlines = end - start;

      for (i = 0; i < scanlines; i++)
	jpeg_read_scanlines (&cinfo, (JSAMPARRAY) &rowbuf[i], 1);

      /*
      for (i = start; i < end; i++)
	gimp_pixel_rgn_set_row (&pixel_rgn, tilerow[i - start], 0, i, drawable->width);
	*/

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      if (preview) /* Add a dummy alpha channel -- convert buf to padded_buf */
	{
	  guchar *dest = padded_buf;
	  guchar *src  = buf;
	  gint num = drawable->width * scanlines;

	  switch (cinfo.output_components)
	    {
	    case 1:
	      for (i=0; i<num; i++)
		{
		  *(dest++) = *(src++);
		  *(dest++) = 255;
		}
	      break;
	    case 3:
	      for (i=0; i<num; i++)
		{
		  *(dest++) = *(src++);
		  *(dest++) = *(src++);
		  *(dest++) = *(src++);
		  *(dest++) = 255;
		}
	      break;
	    default:
	      g_warning ("JPEG - shouldn't have gotten here.  Report to adam@gimp.org");
	    }
	}