gtk2/gdk-pixbuf/io-jpeg.c

/* GdkPixbuf library - JPEG image loader
 *
 * Copyright (C) 1999 Michael Zucchi
 * Copyright (C) 1999 The Free Software Foundation
 * 
 * Progressive loading code Copyright (C) 1999 Red Hat, Inc.
 *
 * Authors: Michael Zucchi <zucchi@zedzone.mmc.com.au>
 *          Federico Mena-Quintero <federico@gimp.org>
 *          Michael Fulbright <drmike@redhat.com>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */


/*
  Progressive file loading notes (11/03/1999) <drmike@redhat.com>...

  These are issues I know of and will be dealing with shortly:

    -  Currently does not handle progressive jpegs - this
       requires a change in the way image_load_increment () calls
       libjpeg. Progressive jpegs are rarer but I will add this
       support asap.

    - error handling is not as good as it should be

 */


#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <setjmp.h>
#include <jpeglib.h>
#include "gdk-pixbuf-private.h"
#include "gdk-pixbuf-io.h"

#ifndef HAVE_SIGSETJMP
#define sigjmp_buf jmp_buf
#define sigsetjmp(jb, x) setjmp(jb)
#define siglongjmp longjmp
#endif


/* we are a "source manager" as far as libjpeg is concerned */
#define JPEG_PROG_BUF_SIZE 65536

typedef struct {
	struct jpeg_source_mgr pub;   /* public fields */

	JOCTET buffer[JPEG_PROG_BUF_SIZE];              /* start of buffer */
	long  skip_next;              /* number of bytes to skip next read */

} my_source_mgr;

typedef my_source_mgr * my_src_ptr;

/* error handler data */
struct error_handler_data {
	struct jpeg_error_mgr pub;
	sigjmp_buf setjmp_buffer;
        GError **error;
};

/* progressive loader context */
typedef struct {
	ModuleUpdatedNotifyFunc  updated_func;
	ModulePreparedNotifyFunc prepared_func;
	gpointer                 user_data;
	
	GdkPixbuf                *pixbuf;
	guchar                   *dptr;   /* current position in pixbuf */

	gboolean                 did_prescan;  /* are we in image data yet? */
	gboolean                 got_header;  /* have we loaded jpeg header? */
	gboolean                 src_initialized;/* TRUE when jpeg lib initialized */
	gboolean                 in_output;   /* did we get suspended in an output pass? */
	struct jpeg_decompress_struct cinfo;
	struct error_handler_data     jerr;
} JpegProgContext;

static GdkPixbuf *gdk_pixbuf__jpeg_image_load (FILE *f, GError **error);
static gpointer gdk_pixbuf__jpeg_image_begin_load (ModulePreparedNotifyFunc func, 
                                                   ModuleUpdatedNotifyFunc func2,
                                                   gpointer user_data,
                                                   GError **error);
static gboolean gdk_pixbuf__jpeg_image_stop_load (gpointer context, GError **error);
static gboolean gdk_pixbuf__jpeg_image_load_increment(gpointer context,
                                                      const guchar *buf, guint size,
                                                      GError **error);


static void
fatal_error_handler (j_common_ptr cinfo)
{
	struct error_handler_data *errmgr;
        char buffer[JMSG_LENGTH_MAX];
        
	errmgr = (struct error_handler_data *) cinfo->err;
        
        /* Create the message */
        (* cinfo->err->format_message) (cinfo, buffer);

        /* broken check for *error == NULL for robustness against
         * crappy JPEG library
         */
        if (errmgr->error && *errmgr->error == NULL) {
                g_set_error (errmgr->error,
                             GDK_PIXBUF_ERROR,
                             GDK_PIXBUF_ERROR_CORRUPT_IMAGE,
                             _("Error interpreting JPEG image file (%s)"),
                             buffer);
        }
        
	siglongjmp (errmgr->setjmp_buffer, 1);

        g_assert_not_reached ();
}

static void
output_message_handler (j_common_ptr cinfo)
{
  /* This method keeps libjpeg from dumping crap to stderr */

  /* do nothing */
}

/* explode gray image data from jpeg library into rgb components in pixbuf */
static void
explode_gray_into_buf (struct jpeg_decompress_struct *cinfo,
		       guchar **lines) 
{
	gint i, j;
	guint w;

	g_return_if_fail (cinfo != NULL);
	g_return_if_fail (cinfo->output_components == 1);

	/* Expand grey->colour.  Expand from the end of the
	 * memory down, so we can use the same buffer.
	 */
	w = cinfo->image_width;
	for (i = cinfo->rec_outbuf_height - 1; i >= 0; i--) {
		guchar *from, *to;
		
		from = lines[i] + w - 1;
		to = lines[i] + (w - 1) * 3;
		for (j = w - 1; j >= 0; j--) {
			to[0] = from[0];
			to[1] = from[0];
			to[2] = from[0];
			to -= 3;
			from--;
		}
	}
}

typedef struct {
  struct jpeg_source_mgr pub;	/* public fields */

  FILE * infile;		/* source stream */
  JOCTET * buffer;		/* start of buffer */
  boolean start_of_file;	/* have we gotten any data yet? */
} stdio_source_mgr;

typedef stdio_source_mgr * stdio_src_ptr;

static void
stdio_init_source (j_decompress_ptr cinfo)
{
  stdio_src_ptr src = (stdio_src_ptr)cinfo->src;
  src->start_of_file = FALSE;
}

static boolean
stdio_fill_input_buffer (j_decompress_ptr cinfo)
{
  stdio_src_ptr src = (stdio_src_ptr) cinfo->src;
  size_t nbytes;

  nbytes = fread (src->buffer, 1, JPEG_PROG_BUF_SIZE, src->infile);

  if (nbytes <= 0) {
#if 0
    if (src->start_of_file)	/* Treat empty input file as fatal error */
      ERREXIT(cinfo, JERR_INPUT_EMPTY);
    WARNMS(cinfo, JWRN_JPEG_EOF);
#endif
    /* Insert a fake EOI marker */
    src->buffer[0] = (JOCTET) 0xFF;
    src->buffer[1] = (JOCTET) JPEG_EOI;
    nbytes = 2;
  }

  src->pub.next_input_byte = src->buffer;
  src->pub.bytes_in_buffer = nbytes;
  src->start_of_file = FALSE;

  return TRUE;
}

static void
stdio_skip_input_data (j_decompress_ptr cinfo, long num_bytes)
{
  stdio_src_ptr src = (stdio_src_ptr) cinfo->src;

  if (num_bytes > 0) {
    while (num_bytes > (long) src->pub.bytes_in_buffer) {
      num_bytes -= (long) src->pub.bytes_in_buffer;
      (void)stdio_fill_input_buffer(cinfo);
    }
    src->pub.next_input_byte += (size_t) num_bytes;
    src->pub.bytes_in_buffer -= (size_t) num_bytes;
  }
}

static void
stdio_term_source (j_decompress_ptr cinfo)
{
}

/* Shared library entry point */
static GdkPixbuf *
gdk_pixbuf__jpeg_image_load (FILE *f, GError **error)
{
	gint i;
	GdkPixbuf * volatile pixbuf = NULL;
	guchar *dptr;
	guchar *lines[4]; /* Used to expand rows, via rec_outbuf_height, 
                           * from the header file: 
                           * " Usually rec_outbuf_height will be 1 or 2, 
                           * at most 4."
			   */
	guchar **lptr;
	struct jpeg_decompress_struct cinfo;
	struct error_handler_data jerr;
	stdio_src_ptr src;

	/* setup error handler */
	cinfo.err = jpeg_std_error (&jerr.pub);
	jerr.pub.error_exit = fatal_error_handler;
        jerr.pub.output_message = output_message_handler;

        jerr.error = error;
        
	if (sigsetjmp (jerr.setjmp_buffer, 1)) {
		/* Whoops there was a jpeg error */
		if (pixbuf)
			g_object_unref (pixbuf);

		jpeg_destroy_decompress (&cinfo);
		return NULL;
	}

	/* load header, setup */
	jpeg_create_decompress (&cinfo);

	cinfo.src = (struct jpeg_source_mgr *)
	  (*cinfo.mem->alloc_small) ((j_common_ptr) &cinfo, JPOOL_PERMANENT,
				  sizeof (stdio_source_mgr));
	src = (stdio_src_ptr) cinfo.src;
	src->buffer = (JOCTET *)
	  (*cinfo.mem->alloc_small) ((j_common_ptr) &cinfo, JPOOL_PERMANENT,
				      JPEG_PROG_BUF_SIZE * sizeof (JOCTET));

	src->pub.init_source = stdio_init_source;
	src->pub.fill_input_buffer = stdio_fill_input_buffer;
	src->pub.skip_input_data = stdio_skip_input_data;
	src->pub.resync_to_restart = jpeg_resync_to_restart; /* use default method */
	src->pub.term_source = stdio_term_source;
	src->infile = f;
	src->pub.bytes_in_buffer = 0; /* forces fill_input_buffer on first read */
	src->pub.next_input_byte = NULL; /* until buffer loaded */

	jpeg_read_header (&cinfo, TRUE);
	jpeg_start_decompress (&cinfo);
	cinfo.do_fancy_upsampling = FALSE;
	cinfo.do_block_smoothing = FALSE;

	pixbuf = gdk_pixbuf_new (GDK_COLORSPACE_RGB, FALSE, 8, cinfo.output_width, cinfo.output_height);
 
	if (!pixbuf) {
		jpeg_destroy_decompress (&cinfo);

                /* broken check for *error == NULL for robustness against
                 * crappy JPEG library
                 */
                if (error && *error == NULL) {
                        g_set_error (error,
                                     GDK_PIXBUF_ERROR,
                                     GDK_PIXBUF_ERROR_INSUFFICIENT_MEMORY,
                                     _("Insufficient memory to load image, try exiting some applications to free memory"));
                }
                
		return NULL;
	}

	dptr = pixbuf->pixels;

	/* decompress all the lines, a few at a time */

	while (cinfo.output_scanline < cinfo.output_height) {
		lptr = lines;
		for (i = 0; i < cinfo.rec_outbuf_height; i++) {
			*lptr++ = dptr;
			dptr += pixbuf->rowstride;
		}

		jpeg_read_scanlines (&cinfo, lines, cinfo.rec_outbuf_height);

		if (cinfo.output_components == 1)
			explode_gray_into_buf (&cinfo, lines);
	}

	jpeg_finish_decompress (&cinfo);
	jpeg_destroy_decompress (&cinfo);

	return pixbuf;
}


/**** Progressive image loading handling *****/

/* these routines required because we are acting as a source manager for */
/* libjpeg. */
static void
init_source (j_decompress_ptr cinfo)
{
	my_src_ptr src = (my_src_ptr) cinfo->src;

	src->skip_next = 0;
}


static void
term_source (j_decompress_ptr cinfo)
{
	/* XXXX - probably should scream something has happened */
}


/* for progressive loading (called "I/O Suspension" by libjpeg docs) */
/* we do nothing except return "FALSE"                               */
static boolean
fill_input_buffer (j_decompress_ptr cinfo)
{
	return FALSE;
}


static void
skip_input_data (j_decompress_ptr cinfo, long num_bytes)
{
	my_src_ptr src = (my_src_ptr) cinfo->src;
	long   num_can_do;

	/* move as far as we can into current buffer */
	/* then set skip_next to catch the rest      */
	if (num_bytes > 0) {
		num_can_do = MIN (src->pub.bytes_in_buffer, num_bytes);
		src->pub.next_input_byte += (size_t) num_can_do;
		src->pub.bytes_in_buffer -= (size_t) num_can_do;

		src->skip_next = num_bytes - num_can_do;
	}
}

 
/* 
 * func - called when we have pixmap created (but no image data)
 * user_data - passed as arg 1 to func
 * return context (opaque to user)
 */

gpointer
gdk_pixbuf__jpeg_image_begin_load (ModulePreparedNotifyFunc prepared_func, 
				   ModuleUpdatedNotifyFunc  updated_func,
				   gpointer user_data,
                                   GError **error)
{
	JpegProgContext *context;
	my_source_mgr   *src;

	context = g_new0 (JpegProgContext, 1);
	context->prepared_func = prepared_func;
	context->updated_func  = updated_func;
	context->user_data = user_data;
	context->pixbuf = NULL;
	context->got_header = FALSE;
	context->did_prescan = FALSE;
	context->src_initialized = FALSE;
	context->in_output = FALSE;

	/* create libjpeg structures */
	jpeg_create_decompress (&context->cinfo);

	context->cinfo.src = (struct jpeg_source_mgr *) g_try_malloc (sizeof (my_source_mgr));
	if (!context->cinfo.src) {
	  g_set_error (error,
		       GDK_PIXBUF_ERROR,
		       GDK_PIXBUF_ERROR_INSUFFICIENT_MEMORY,
		       _("Couldn't allocate memory for loading JPEG file"));
	  return NULL;
	}
	memset (context->cinfo.src, 0, sizeof (my_source_mgr));
       
	src = (my_src_ptr) context->cinfo.src;

	context->cinfo.err = jpeg_std_error (&context->jerr.pub);
	context->jerr.pub.error_exit = fatal_error_handler;
        context->jerr.pub.output_message = output_message_handler;
        context->jerr.error = error;
        
	src = (my_src_ptr) context->cinfo.src;
	src->pub.init_source = init_source;
	src->pub.fill_input_buffer = fill_input_buffer;
	src->pub.skip_input_data = skip_input_data;
	src->pub.resync_to_restart = jpeg_resync_to_restart;
	src->pub.term_source = term_source;
	src->pub.bytes_in_buffer = 0;
	src->pub.next_input_byte = NULL;

        context->jerr.error = NULL;
        
	return (gpointer) context;
}

/*
 * context - returned from image_begin_load
 *
 * free context, unref gdk_pixbuf
 */
static gboolean
gdk_pixbuf__jpeg_image_stop_load (gpointer data, GError **error)
{
	JpegProgContext *context = (JpegProgContext *) data;

	g_return_val_if_fail (context != NULL, TRUE);

        /* FIXME this thing needs to report errors if
         * we have unused image data
         */
        
	if (context->pixbuf)
		g_object_unref (context->pixbuf);

	/* if we have an error? */
	if (sigsetjmp (context->jerr.setjmp_buffer, 1)) {
		jpeg_destroy_decompress (&context->cinfo);
	} else {
		jpeg_finish_decompress(&context->cinfo);
		jpeg_destroy_decompress(&context->cinfo);
	}

	if (context->cinfo.src) {
		my_src_ptr src = (my_src_ptr) context->cinfo.src;
		
		g_free (src);
	}

	g_free (context);

        return TRUE;
}




/*
 * context - from image_begin_load
 * buf - new image data
 * size - length of new image data
 *
 * append image data onto inrecrementally built output image
 */
static gboolean
gdk_pixbuf__jpeg_image_load_increment (gpointer data,
                                       const guchar *buf, guint size,
                                       GError **error)
{
	JpegProgContext *context = (JpegProgContext *)data;
	struct jpeg_decompress_struct *cinfo;
	my_src_ptr  src;
	guint       num_left, num_copy;
	guint       last_bytes_left;
	guint       spinguard;
	gboolean    first;
	const guchar *bufhd;

	g_return_val_if_fail (context != NULL, FALSE);
	g_return_val_if_fail (buf != NULL, FALSE);

	src = (my_src_ptr) context->cinfo.src;

	cinfo = &context->cinfo;

        context->jerr.error = error;
        
	/* XXXXXXX (drmike) - loop(s) below need to be recoded now I
         *                    have a grasp of what the flow needs to be!
         */

	/* check for fatal error */
	if (sigsetjmp (context->jerr.setjmp_buffer, 1)) {
		return FALSE;
	}

	/* skip over data if requested, handle unsigned int sizes cleanly */
	/* only can happen if we've already called jpeg_get_header once   */
	if (context->src_initialized && src->skip_next) {
		if (src->skip_next > size) {
			src->skip_next -= size;
			return TRUE;
		} else {
			num_left = size - src->skip_next;
			bufhd = buf + src->skip_next;
			src->skip_next = 0;
		}
	} else {
		num_left = size;
		bufhd = buf;
	}

	if (num_left == 0)
		return TRUE;

	last_bytes_left = 0;
	spinguard = 0;
	first = TRUE;
	while (TRUE) {

		/* handle any data from caller we haven't processed yet */
		if (num_left > 0) {
			if(src->pub.bytes_in_buffer && 
			   src->pub.next_input_byte != src->buffer)
				memmove(src->buffer, src->pub.next_input_byte,
					src->pub.bytes_in_buffer);


			num_copy = MIN (JPEG_PROG_BUF_SIZE - src->pub.bytes_in_buffer,
					num_left);

			memcpy(src->buffer + src->pub.bytes_in_buffer, bufhd,num_copy);
			src->pub.next_input_byte = src->buffer;
			src->pub.bytes_in_buffer += num_copy;
			bufhd += num_copy;
			num_left -= num_copy;
		} else {
		/* did anything change from last pass, if not return */
			if (first) {
				last_bytes_left = src->pub.bytes_in_buffer;
				first = FALSE;
			} else if (src->pub.bytes_in_buffer == last_bytes_left)
				spinguard++;
			else
				last_bytes_left = src->pub.bytes_in_buffer;
		}

		/* should not go through twice and not pull bytes out of buf */
		if (spinguard > 2)
			return TRUE;

		/* try to load jpeg header */
		if (!context->got_header) {
			int rc;

			rc = jpeg_read_header (cinfo, TRUE);
			context->src_initialized = TRUE;

			if (rc == JPEG_SUSPENDED)
				continue;

			context->got_header = TRUE;

			context->pixbuf = gdk_pixbuf_new(GDK_COLORSPACE_RGB, 
							 FALSE,
							 8, 
							 cinfo->image_width,
							 cinfo->image_height);

			if (context->pixbuf == NULL) {
                                g_set_error (error,
                                             GDK_PIXBUF_ERROR,
                                             GDK_PIXBUF_ERROR_INSUFFICIENT_MEMORY,
                                             _("Couldn't allocate memory for loading JPEG file"));
                                return FALSE;
			}

			/* Use pixbuf buffer to store decompressed data */
			context->dptr = context->pixbuf->pixels;

			/* Notify the client that we are ready to go */
			(* context->prepared_func) (context->pixbuf,
                                                    NULL,
						    context->user_data);

		} else if (!context->did_prescan) {
			int rc;
			
			/* start decompression */
			cinfo->buffered_image = TRUE;
			rc = jpeg_start_decompress (cinfo);
			cinfo->do_fancy_upsampling = FALSE;
			cinfo->do_block_smoothing = FALSE;
			
			if (rc == JPEG_SUSPENDED)
				continue;

			context->did_prescan = TRUE;
		} else {
			/* we're decompressing so feed jpeg lib scanlines */
			guchar *lines[4];
			guchar **lptr;
			guchar *rowptr;
			gint   nlines, i;

			/* keep going until we've done all passes */
			while (!jpeg_input_complete (cinfo)) {
				if (!context->in_output) {
					if (jpeg_start_output (cinfo, cinfo->input_scan_number)) {
						context->in_output = TRUE;
						context->dptr = context->pixbuf->pixels;
					}
					else
						break;
				}
				/* keep going until we've done all scanlines */
				while (cinfo->output_scanline < cinfo->output_height) {
					lptr = lines;
					rowptr = context->dptr;
					for (i=0; i < cinfo->rec_outbuf_height; i++) {
						*lptr++ = rowptr;
						rowptr += context->pixbuf->rowstride;
					}
					
					nlines = jpeg_read_scanlines (cinfo, lines,
								      cinfo->rec_outbuf_height);
					if (nlines == 0)
						break;

				        /* handle gray */
					if (cinfo->output_components == 1)
						explode_gray_into_buf (cinfo, lines);
					
					context->dptr += nlines * context->pixbuf->rowstride;
					
				        /* send updated signal */
					(* context->updated_func) (context->pixbuf,
								   0, 
								   cinfo->output_scanline-1,
								   cinfo->image_width, 
								   nlines,
								   context->user_data);
				}
				if (cinfo->output_scanline >= cinfo->output_height && 
				    jpeg_finish_output (cinfo))
					context->in_output = FALSE;
				else
					break;
			}
			if (jpeg_input_complete (cinfo))
				/* did entire image */
				return TRUE;
			else
				continue;
		}
	}

	return TRUE;
}

static gboolean
gdk_pixbuf__jpeg_image_save (FILE          *f, 
                             GdkPixbuf     *pixbuf, 
                             gchar        **keys,
                             gchar        **values,
                             GError       **error)
{
        /* FIXME error handling is broken */
        
       struct jpeg_compress_struct cinfo;
       guchar *buf = NULL;
       guchar *ptr;
       guchar *pixels = NULL;
       JSAMPROW *jbuf;
       int y = 0;
       volatile int quality = 75; /* default; must be between 0 and 100 */
       int i, j;
       int w, h = 0;
       int rowstride = 0;
       struct error_handler_data jerr;

       if (keys && *keys) {
               gchar **kiter = keys;
               gchar **viter = values;

               while (*kiter) {
                       if (strcmp (*kiter, "quality") == 0) {
                               char *endptr = NULL;
                               quality = strtol (*viter, &endptr, 10);

                               if (endptr == *viter) {
                                       g_set_error (error,
                                                    GDK_PIXBUF_ERROR,
                                                    GDK_PIXBUF_ERROR_BAD_OPTION,
                                                    _("JPEG quality must be a value between 0 and 100; value '%s' could not be parsed."),
                                                    *viter);

                                       return FALSE;
                               }
                               
                               if (quality < 0 ||
                                   quality > 100) {
                                       /* This is a user-visible error;
                                        * lets people skip the range-checking
                                        * in their app.
                                        */
                                       g_set_error (error,
                                                    GDK_PIXBUF_ERROR,
                                                    GDK_PIXBUF_ERROR_BAD_OPTION,
                                                    _("JPEG quality must be a value between 0 and 100; value '%d' is not allowed."),
                                                    quality);

                                       return FALSE;
                               }
                       } else {
                               g_warning ("Bad option name '%s' passed to JPEG saver",
                                          *kiter);
                               return FALSE;
                       }
               
                       ++kiter;
                       ++viter;
               }
       }
       
       rowstride = gdk_pixbuf_get_rowstride (pixbuf);

       w = gdk_pixbuf_get_width (pixbuf);
       h = gdk_pixbuf_get_height (pixbuf);

       /* no image data? abort */
       pixels = gdk_pixbuf_get_pixels (pixbuf);
       g_return_val_if_fail (pixels != NULL, FALSE);

       /* allocate a small buffer to convert image data */
       buf = g_try_malloc (w * 3 * sizeof (guchar));
       if (!buf) {
	       g_set_error (error,
			    GDK_PIXBUF_ERROR,
			    GDK_PIXBUF_ERROR_INSUFFICIENT_MEMORY,
			    _("Couldn't allocate memory for loading JPEG file"));
	       return FALSE;
       }

       /* set up error handling */
       jerr.pub.error_exit = fatal_error_handler;
       jerr.pub.output_message = output_message_handler;
       jerr.error = error;
       
       cinfo.err = jpeg_std_error (&(jerr.pub));
       if (sigsetjmp (jerr.setjmp_buffer, 1)) {
               jpeg_destroy_compress (&cinfo);
               g_free (buf);
               return FALSE;
       }

       /* setup compress params */
       jpeg_create_compress (&cinfo);
       jpeg_stdio_dest (&cinfo, f);
       cinfo.image_width      = w;
       cinfo.image_height     = h;
       cinfo.input_components = 3; 
       cinfo.in_color_space   = JCS_RGB;

       /* set up jepg compression parameters */
       jpeg_set_defaults (&cinfo);
       jpeg_set_quality (&cinfo, quality, TRUE);
       jpeg_start_compress (&cinfo, TRUE);
       /* get the start pointer */
       ptr = pixels;
       /* go one scanline at a time... and save */
       i = 0;
       while (cinfo.next_scanline < cinfo.image_height) {
               /* convert scanline from ARGB to RGB packed */
               for (j = 0; j < w; j++)
                       memcpy (&(buf[j*3]), &(ptr[i*rowstride + j*3]), 3);

               /* write scanline */
               jbuf = (JSAMPROW *)(&buf);
               jpeg_write_scanlines (&cinfo, jbuf, 1);
               i++;
               y++;

       }
       
       /* finish off */
       jpeg_finish_compress (&cinfo);   
       g_free (buf);
       return TRUE;
}

void
gdk_pixbuf__jpeg_fill_vtable (GdkPixbufModule *module)
{
  module->load = gdk_pixbuf__jpeg_image_load;
  module->begin_load = gdk_pixbuf__jpeg_image_begin_load;
  module->stop_load = gdk_pixbuf__jpeg_image_stop_load;
  module->load_increment = gdk_pixbuf__jpeg_image_load_increment;
  module->save = gdk_pixbuf__jpeg_image_save;
}