]> Pileus Git - ~andy/gtk/blobdiff - gdk-pixbuf/io-jpeg.c
Updated Slovenian translation
[~andy/gtk] / gdk-pixbuf / io-jpeg.c
index 85d75dfe60be264603b8b90e73ebbe8a1f700e48..da59386c164daa4f1a06b15d9d536405fb2b47ea 100644 (file)
  */
 
 
-#include <config.h>
+#include "config.h"
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <setjmp.h>
 #include <jpeglib.h>
+#include <jerror.h>
 #include "gdk-pixbuf-private.h"
 #include "gdk-pixbuf-io.h"
 
@@ -110,7 +111,9 @@ fatal_error_handler (j_common_ptr cinfo)
         if (errmgr->error && *errmgr->error == NULL) {
                 g_set_error (errmgr->error,
                              GDK_PIXBUF_ERROR,
-                             GDK_PIXBUF_ERROR_CORRUPT_IMAGE,
+                             cinfo->err->msg_code == JERR_OUT_OF_MEMORY 
+                            ? GDK_PIXBUF_ERROR_INSUFFICIENT_MEMORY 
+                            : GDK_PIXBUF_ERROR_CORRUPT_IMAGE,
                              _("Error interpreting JPEG image file (%s)"),
                              buffer);
         }
@@ -274,11 +277,181 @@ colorspace_name (const J_COLOR_SPACE jpeg_color_space)
        }
 }
 
+
+const char leth[]  = {0x49, 0x49, 0x2a, 0x00}; // Little endian TIFF header
+const char beth[]  = {0x4d, 0x4d, 0x00, 0x2a}; // Big endian TIFF header
+const char types[] = {0x00, 0x01, 0x01, 0x02, 0x04, 0x08, 0x00, 
+                     0x08, 0x00, 0x04, 0x08};  // size in bytes for EXIF types
+#define DE_ENDIAN16(val) endian == G_BIG_ENDIAN ? GUINT16_FROM_BE(val) : GUINT16_FROM_LE(val)
+#define DE_ENDIAN32(val) endian == G_BIG_ENDIAN ? GUINT32_FROM_BE(val) : GUINT32_FROM_LE(val)
+#define ENDIAN16_IT(val) endian == G_BIG_ENDIAN ? GUINT16_TO_BE(val) : GUINT16_TO_LE(val)
+#define ENDIAN32_IT(val) endian == G_BIG_ENDIAN ? GUINT32_TO_BE(val) : GUINT32_TO_LE(val)
+#define EXIF_JPEG_MARKER   JPEG_APP0+1
+#define EXIF_IDENT_STRING  "Exif\000\000"
+
+static unsigned short de_get16(void *ptr, guint endian)
+{
+       unsigned short val;
+
+       memcpy(&val, ptr, sizeof(val));
+       val = DE_ENDIAN16(val);
+
+       return val;
+}
+
+static unsigned int de_get32(void *ptr, guint endian)
+{
+       unsigned int val;
+
+       memcpy(&val, ptr, sizeof(val));
+       val = DE_ENDIAN32(val);
+
+       return val;
+}
+
+static gint 
+get_orientation (j_decompress_ptr cinfo)
+{
+       /* This function looks through the meta data in the libjpeg decompress structure to
+          determine if an EXIF Orientation tag is present and if so return its value (1-8). 
+          If no EXIF Orientation tag is found 0 (zero) is returned. */
+
+       guint   i;              /* index into working buffer */
+       guint   orient_tag_id;  /* endianed version of orientation tag ID */
+       guint   ret;            /* Return value */
+       guint   offset;         /* de-endianed offset in various situations */
+       guint   tags;           /* number of tags in current ifd */
+       guint   type;           /* de-endianed type of tag used as index into types[] */
+       guint   count;          /* de-endianed count of elements in a tag */
+        guint   tiff = 0;      /* offset to active tiff header */
+        guint   endian = 0;    /* detected endian of data */
+
+       jpeg_saved_marker_ptr exif_marker;  /* Location of the Exif APP1 marker */
+       jpeg_saved_marker_ptr cmarker;      /* Location to check for Exif APP1 marker */
+
+       /* check for Exif marker (also called the APP1 marker) */
+       exif_marker = NULL;
+       cmarker = cinfo->marker_list;
+       while (cmarker) {
+               if (cmarker->marker == EXIF_JPEG_MARKER) {
+                       /* The Exif APP1 marker should contain a unique
+                          identification string ("Exif\0\0"). Check for it. */
+                       if (!memcmp (cmarker->data, EXIF_IDENT_STRING, 6)) {
+                               exif_marker = cmarker;
+                               }
+                       }
+               cmarker = cmarker->next;
+       }
+         
+       /* Did we find the Exif APP1 marker? */
+       if (exif_marker == NULL)
+               return 0;
+
+       /* Do we have enough data? */
+       if (exif_marker->data_length < 32)
+               return 0;
+
+        /* Check for TIFF header and catch endianess */
+       i = 0;
+
+       /* Just skip data until TIFF header - it should be within 16 bytes from marker start.
+          Normal structure relative to APP1 marker -
+               0x0000: APP1 marker entry = 2 bytes
+               0x0002: APP1 length entry = 2 bytes
+               0x0004: Exif Identifier entry = 6 bytes
+               0x000A: Start of TIFF header (Byte order entry) - 4 bytes  
+                       - This is what we look for, to determine endianess.
+               0x000E: 0th IFD offset pointer - 4 bytes
+
+               exif_marker->data points to the first data after the APP1 marker
+               and length entries, which is the exif identification string.
+               The TIFF header should thus normally be found at i=6, below,
+               and the pointer to IFD0 will be at 6+4 = 10.
+       */
+                   
+       while (i < 16) {
+               /* Little endian TIFF header */
+               if (memcmp (&exif_marker->data[i], leth, 4) == 0){ 
+                       endian = G_LITTLE_ENDIAN;
+                }
+               /* Big endian TIFF header */
+               else if (memcmp (&exif_marker->data[i], beth, 4) == 0){ 
+                       endian = G_BIG_ENDIAN;
+                }
+               /* Keep looking through buffer */
+               else {
+                       i++;
+                       continue;
+               }
+               /* We have found either big or little endian TIFF header */
+               tiff = i;
+               break;
+        }
+
+       /* So did we find a TIFF header or did we just hit end of buffer? */
+       if (tiff == 0) 
+               return 0;
+        /* Endian the orientation tag ID, to locate it more easily */
+        orient_tag_id = ENDIAN16_IT(0x112);
+        /* Read out the offset pointer to IFD0 */
+        offset  = de_get32(&exif_marker->data[i] + 4, endian);
+       i       = i + offset;
+
+       /* Check that we still are within the buffer and can read the tag count */
+       if ((i + 2) > exif_marker->data_length)
+               return 0;
+
+       /* Find out how many tags we have in IFD0. As per the TIFF spec, the first
+          two bytes of the IFD contain a count of the number of tags. */
+       tags    = de_get16(&exif_marker->data[i], endian);
+       i       = i + 2;
+
+       /* Check that we still have enough data for all tags to check. The tags
+          are listed in consecutive 12-byte blocks. The tag ID, type, size, and
+          a pointer to the actual value, are packed into these 12 byte entries. */
+       if ((i + tags * 12) > exif_marker->data_length)
+               return 0;
+
+       /* Check through IFD0 for tags of interest */
+       while (tags--){
+               type   = de_get16(&exif_marker->data[i + 2], endian);
+               count  = de_get32(&exif_marker->data[i + 4], endian);
+
+               /* Is this the orientation tag? */
+               if (memcmp (&exif_marker->data[i], (char *) &orient_tag_id, 2) == 0){ 
+                       /* Check that type and count fields are OK. The orientation field 
+                          will consist of a single (count=1) 2-byte integer (type=3). */
+                       if (type != 3 || count != 1) return 0;
+
+                       /* Return the orientation value. Within the 12-byte block, the
+                          pointer to the actual data is at offset 8. */
+                       ret =  de_get16(&exif_marker->data[i + 8], endian);
+                       return ret <= 8 ? ret : 0;
+               }
+               /* move the pointer to the next 12-byte tag field. */
+               i = i + 12;
+       }
+
+       return 0; /* No EXIF Orientation tag found */
+}
+
+
 /* Shared library entry point */
 static GdkPixbuf *
 gdk_pixbuf__jpeg_image_load (FILE *f, GError **error)
 {
-       gint i;
+       gint   i;
+       int     is_otag;
+       char   otag_str[5];
        GdkPixbuf * volatile pixbuf = NULL;
        guchar *dptr;
        guchar *lines[4]; /* Used to expand rows, via rec_outbuf_height, 
@@ -304,6 +477,8 @@ gdk_pixbuf__jpeg_image_load (FILE *f, GError **error)
                        g_object_unref (pixbuf);
 
                jpeg_destroy_decompress (&cinfo);
+
+               /* error should have been set by fatal_error_handler () */
                return NULL;
        }
 
@@ -327,7 +502,12 @@ gdk_pixbuf__jpeg_image_load (FILE *f, GError **error)
        src->pub.bytes_in_buffer = 0; /* forces fill_input_buffer on first read */
        src->pub.next_input_byte = NULL; /* until buffer loaded */
 
+       jpeg_save_markers (&cinfo, EXIF_JPEG_MARKER, 0xffff);
        jpeg_read_header (&cinfo, TRUE);
+
+       /* check for orientation tag */
+       is_otag = get_orientation (&cinfo);
+       
        jpeg_start_decompress (&cinfo);
        cinfo.do_fancy_upsampling = FALSE;
        cinfo.do_block_smoothing = FALSE;
@@ -343,15 +523,22 @@ gdk_pixbuf__jpeg_image_load (FILE *f, GError **error)
                  * 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"));
+                        g_set_error_literal (error,
+                                             GDK_PIXBUF_ERROR,
+                                             GDK_PIXBUF_ERROR_INSUFFICIENT_MEMORY,
+                                             _("Insufficient memory to load image, try exiting some applications to free memory"));
                 }
                 
                return NULL;
        }
 
+       /* if orientation tag was found set an option to remember its value */
+       if (is_otag) {
+               g_snprintf (otag_str, sizeof (otag_str), "%d", is_otag);
+               gdk_pixbuf_set_option (pixbuf, "orientation", otag_str);
+       }
+
+
        dptr = pixbuf->pixels;
 
        /* decompress all the lines, a few at a time */
@@ -475,10 +662,10 @@ gdk_pixbuf__jpeg_image_begin_load (GdkPixbufModuleSizeFunc size_func,
 
        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"));
+               g_set_error_literal (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));
@@ -513,6 +700,7 @@ static gboolean
 gdk_pixbuf__jpeg_image_stop_load (gpointer data, GError **error)
 {
        JpegProgContext *context = (JpegProgContext *) data;
+        gboolean retval;
 
        g_return_val_if_fail (context != NULL, TRUE);
        
@@ -524,13 +712,16 @@ gdk_pixbuf__jpeg_image_stop_load (gpointer data, GError **error)
                g_object_unref (context->pixbuf);
        
        /* if we have an error? */
+       context->jerr.error = error;
        if (sigsetjmp (context->jerr.setjmp_buffer, 1)) {
-               jpeg_destroy_decompress (&context->cinfo);
+                retval = FALSE;
        } else {
-               jpeg_finish_decompress(&context->cinfo);
-               jpeg_destroy_decompress(&context->cinfo);
+               jpeg_finish_decompress (&context->cinfo);
+                retval = TRUE;
        }
 
+        jpeg_destroy_decompress (&context->cinfo);
+
        if (context->cinfo.src) {
                my_src_ptr src = (my_src_ptr) context->cinfo.src;
                
@@ -539,10 +730,70 @@ gdk_pixbuf__jpeg_image_stop_load (gpointer data, GError **error)
 
        g_free (context);
 
-        return TRUE;
+        return retval;
 }
 
 
+static gboolean
+gdk_pixbuf__jpeg_image_load_lines (JpegProgContext  *context,
+                                   GError          **error)
+{
+        struct jpeg_decompress_struct *cinfo = &context->cinfo;
+        guchar *lines[4];
+        guchar **lptr;
+        guchar *rowptr;
+        gint   nlines, i;
+
+        /* 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;
+
+                switch (cinfo->out_color_space) {
+                case JCS_GRAYSCALE:
+                        explode_gray_into_buf (cinfo, lines);
+                        break;
+                case JCS_RGB:
+                        /* do nothing */
+                        break;
+                case JCS_CMYK:
+                        convert_cmyk_to_rgb (cinfo, lines);
+                        break;
+                default:
+                        if (error && *error == NULL) {
+                                g_set_error (error,
+                                             GDK_PIXBUF_ERROR,
+                                             GDK_PIXBUF_ERROR_UNKNOWN_TYPE,
+                                             _("Unsupported JPEG color space (%s)"),
+                                             colorspace_name (cinfo->out_color_space));
+                        }
+
+                        return FALSE;
+                }
+
+                context->dptr += nlines * context->pixbuf->rowstride;
+
+                /* send updated signal */
+               if (context->updated_func)
+                       (* context->updated_func) (context->pixbuf,
+                                                  0,
+                                                  cinfo->output_scanline - 1,
+                                                  cinfo->image_width,
+                                                  nlines,
+                                                  context->user_data);
+        }
+
+        return TRUE;
+}
 
 
 /*
@@ -558,14 +809,16 @@ gdk_pixbuf__jpeg_image_load_increment (gpointer data,
                                        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;
-       gint        width, height;
+       struct           jpeg_decompress_struct *cinfo;
+       my_src_ptr       src;
+       guint            num_left, num_copy;
+       guint            last_num_left, last_bytes_left;
+       guint            spinguard;
+       gboolean         first;
+       const guchar    *bufhd;
+       gint             width, height;
+        int              is_otag;
+       char             otag_str[5];
 
        g_return_val_if_fail (context != NULL, FALSE);
        g_return_val_if_fail (buf != NULL, FALSE);
@@ -600,6 +853,7 @@ gdk_pixbuf__jpeg_image_load_increment (gpointer data,
        if (num_left == 0)
                return TRUE;
 
+       last_num_left = num_left;
        last_bytes_left = 0;
        spinguard = 0;
        first = TRUE;
@@ -621,15 +875,18 @@ gdk_pixbuf__jpeg_image_load_increment (gpointer data,
                        src->pub.bytes_in_buffer += num_copy;
                        bufhd += num_copy;
                        num_left -= num_copy;
+               }
+
+                /* 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
+                          && num_left == last_num_left) {
+                        spinguard++;
                } 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;
+                        last_bytes_left = src->pub.bytes_in_buffer;
+                       last_num_left = num_left;
                }
 
                /* should not go through twice and not pull bytes out of buf */
@@ -639,7 +896,8 @@ gdk_pixbuf__jpeg_image_load_increment (gpointer data,
                /* try to load jpeg header */
                if (!context->got_header) {
                        int rc;
-                       
+               
+                       jpeg_save_markers (cinfo, EXIF_JPEG_MARKER, 0xffff);
                        rc = jpeg_read_header (cinfo, TRUE);
                        context->src_initialized = TRUE;
                        
@@ -647,13 +905,21 @@ gdk_pixbuf__jpeg_image_load_increment (gpointer data,
                                continue;
                        
                        context->got_header = TRUE;
-                       
+
+                       /* check for orientation tag */
+                       is_otag = get_orientation (cinfo);
+               
                        width = cinfo->image_width;
                        height = cinfo->image_height;
                        if (context->size_func) {
                                (* context->size_func) (&width, &height, context->user_data);
-                               if (width == 0 || height == 0)
+                               if (width == 0 || height == 0) {
+                                       g_set_error_literal (error,
+                                                             GDK_PIXBUF_ERROR,
+                                                             GDK_PIXBUF_ERROR_CORRUPT_IMAGE,
+                                                             _("Transformed JPEG has zero width or height."));
                                        return FALSE;
+                               }
                        }
                        
                        for (cinfo->scale_denom = 2; cinfo->scale_denom <= 8; cinfo->scale_denom *= 2) {
@@ -672,26 +938,33 @@ gdk_pixbuf__jpeg_image_load_increment (gpointer data,
                                                          cinfo->output_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"));
+                                g_set_error_literal (error,
+                                                     GDK_PIXBUF_ERROR,
+                                                     GDK_PIXBUF_ERROR_INSUFFICIENT_MEMORY,
+                                                     _("Couldn't allocate memory for loading JPEG file"));
                                 return FALSE;
                        }
-                       
+               
+                       /* if orientation tag was found set an option to remember its value */
+                       if (is_otag) {
+                               g_snprintf (otag_str, sizeof (otag_str), "%d", is_otag);
+                               gdk_pixbuf_set_option (context->pixbuf, "orientation", otag_str);
+                       }
+
                        /* 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);
+                       if (context->prepared_func)
+                               (* context->prepared_func) (context->pixbuf,
+                                                           NULL,
+                                                           context->user_data);
                        
                } else if (!context->did_prescan) {
                        int rc;                 
                        
                        /* start decompression */
-                       cinfo->buffered_image = TRUE;
+                       cinfo->buffered_image = cinfo->progressive_mode;
                        rc = jpeg_start_decompress (cinfo);
                        cinfo->do_fancy_upsampling = FALSE;
                        cinfo->do_block_smoothing = FALSE;
@@ -700,12 +973,20 @@ gdk_pixbuf__jpeg_image_load_increment (gpointer data,
                                continue;
 
                        context->did_prescan = TRUE;
+               } else if (!cinfo->buffered_image) {
+                        /* we're decompressing unbuffered so
+                         * simply get scanline by scanline from jpeg lib
+                         */
+                        if (! gdk_pixbuf__jpeg_image_load_lines (context,
+                                                                 error))
+                                return FALSE;
+
+                       if (cinfo->output_scanline >= cinfo->output_height)
+                               return TRUE;
                } else {
-                       /* we're decompressing so feed jpeg lib scanlines */
-                       guchar *lines[4];
-                       guchar **lptr;
-                       guchar *rowptr;
-                       gint   nlines, i;
+                        /* we're decompressing buffered (progressive)
+                         * so feed jpeg lib scanlines
+                         */
 
                        /* keep going until we've done all passes */
                        while (!jpeg_input_complete (cinfo)) {
@@ -717,53 +998,13 @@ gdk_pixbuf__jpeg_image_load_increment (gpointer data,
                                        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;
 
-                                       switch (cinfo->out_color_space) {
-                                           case JCS_GRAYSCALE:
-                                                   explode_gray_into_buf (cinfo, lines);
-                                                   break;
-                                           case JCS_RGB:
-                                                   /* do nothing */
-                                                   break;
-                                           case JCS_CMYK:
-                                                   convert_cmyk_to_rgb (cinfo, lines);
-                                                   break;
-                                           default:
-                                                   if (error && *error == NULL) {
-                                                           g_set_error (error,
-                                                                        GDK_PIXBUF_ERROR,
-                                                                        GDK_PIXBUF_ERROR_UNKNOWN_TYPE,
-                                                                        _("Unsupported JPEG color space (%s)"),
-                                                                        colorspace_name (cinfo->out_color_space)); 
-                                                   }
-                                                   
-                                                   return FALSE;
-                                       }
+                                /* get scanlines from jpeg lib */
+                                if (! gdk_pixbuf__jpeg_image_load_lines (context,
+                                                                         error))
+                                        return FALSE;
 
-                                       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 && 
+                               if (cinfo->output_scanline >= cinfo->output_height &&
                                    jpeg_finish_output (cinfo))
                                        context->in_output = FALSE;
                                else
@@ -776,16 +1017,87 @@ gdk_pixbuf__jpeg_image_load_increment (gpointer data,
                                continue;
                }
        }
+}
+
+/* Save */
+
+#define TO_FUNCTION_BUF_SIZE 4096
+
+typedef struct {
+       struct jpeg_destination_mgr pub;
+       JOCTET             *buffer;
+       GdkPixbufSaveFunc   save_func;
+       gpointer            user_data;
+       GError            **error;
+} ToFunctionDestinationManager;
+
+void
+to_callback_init (j_compress_ptr cinfo)
+{
+       ToFunctionDestinationManager *destmgr;
+
+       destmgr = (ToFunctionDestinationManager*) cinfo->dest;
+       destmgr->pub.next_output_byte = destmgr->buffer;
+       destmgr->pub.free_in_buffer = TO_FUNCTION_BUF_SIZE;
+}
+
+static void
+to_callback_do_write (j_compress_ptr cinfo, gsize length)
+{
+       ToFunctionDestinationManager *destmgr;
+
+       destmgr = (ToFunctionDestinationManager*) cinfo->dest;
+        if (!destmgr->save_func (destmgr->buffer,
+                                length,
+                                destmgr->error,
+                                destmgr->user_data)) {
+               struct error_handler_data *errmgr;
+        
+               errmgr = (struct error_handler_data *) cinfo->err;
+               /* Use a default error message if the callback didn't set one,
+                * which it should have.
+                */
+               if (errmgr->error && *errmgr->error == NULL) {
+                       g_set_error_literal (errmgr->error,
+                                             GDK_PIXBUF_ERROR,
+                                             GDK_PIXBUF_ERROR_CORRUPT_IMAGE,
+                                             "write function failed");
+               }
+               siglongjmp (errmgr->setjmp_buffer, 1);
+               g_assert_not_reached ();
+        }
+}
 
+static boolean
+to_callback_empty_output_buffer (j_compress_ptr cinfo)
+{
+       ToFunctionDestinationManager *destmgr;
+
+       destmgr = (ToFunctionDestinationManager*) cinfo->dest;
+       to_callback_do_write (cinfo, TO_FUNCTION_BUF_SIZE);
+       destmgr->pub.next_output_byte = destmgr->buffer;
+       destmgr->pub.free_in_buffer = TO_FUNCTION_BUF_SIZE;
        return TRUE;
 }
 
+void
+to_callback_terminate (j_compress_ptr cinfo)
+{
+       ToFunctionDestinationManager *destmgr;
+
+       destmgr = (ToFunctionDestinationManager*) cinfo->dest;
+       to_callback_do_write (cinfo, TO_FUNCTION_BUF_SIZE - destmgr->pub.free_in_buffer);
+}
+
 static gboolean
-gdk_pixbuf__jpeg_image_save (FILE          *f, 
-                             GdkPixbuf     *pixbuf, 
-                             gchar        **keys,
-                             gchar        **values,
-                             GError       **error)
+real_save_jpeg (GdkPixbuf          *pixbuf,
+               gchar             **keys,
+               gchar             **values,
+               GError            **error,
+               gboolean            to_callback,
+               FILE               *f,
+               GdkPixbufSaveFunc   save_func,
+               gpointer            user_data)
 {
         /* FIXME error handling is broken */
         
@@ -799,7 +1111,11 @@ gdk_pixbuf__jpeg_image_save (FILE          *f,
        int i, j;
        int w, h = 0;
        int rowstride = 0;
+       int n_channels;
        struct error_handler_data jerr;
+       ToFunctionDestinationManager to_callback_destmgr;
+
+       to_callback_destmgr.buffer = NULL;
 
        if (keys && *keys) {
                gchar **kiter = keys;
@@ -835,9 +1151,7 @@ gdk_pixbuf__jpeg_image_save (FILE          *f,
                                        return FALSE;
                                }
                        } else {
-                               g_warning ("Bad option name '%s' passed to JPEG saver",
-                                          *kiter);
-                               return FALSE;
+                               g_warning ("Unrecognized parameter (%s) passed to JPEG saver.", *kiter);
                        }
                
                        ++kiter;
@@ -846,23 +1160,33 @@ gdk_pixbuf__jpeg_image_save (FILE          *f,
        }
        
        rowstride = gdk_pixbuf_get_rowstride (pixbuf);
+       n_channels = gdk_pixbuf_get_n_channels (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 */
+       /* Allocate a small buffer to convert image data,
+       * and a larger buffer if doing to_callback save.
+       */
        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"));
+              g_set_error_literal (error,
+                                    GDK_PIXBUF_ERROR,
+                                    GDK_PIXBUF_ERROR_INSUFFICIENT_MEMORY,
+                                    _("Couldn't allocate memory for loading JPEG file"));
               return FALSE;
        }
+       if (to_callback) {
+              to_callback_destmgr.buffer = g_try_malloc (TO_FUNCTION_BUF_SIZE);
+              if (!to_callback_destmgr.buffer) {
+                      g_set_error_literal (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;
@@ -873,12 +1197,23 @@ gdk_pixbuf__jpeg_image_save (FILE          *f,
        if (sigsetjmp (jerr.setjmp_buffer, 1)) {
                jpeg_destroy_compress (&cinfo);
                g_free (buf);
+              g_free (to_callback_destmgr.buffer);
                return FALSE;
        }
 
        /* setup compress params */
        jpeg_create_compress (&cinfo);
-       jpeg_stdio_dest (&cinfo, f);
+       if (to_callback) {
+              to_callback_destmgr.pub.init_destination    = to_callback_init;
+              to_callback_destmgr.pub.empty_output_buffer = to_callback_empty_output_buffer;
+              to_callback_destmgr.pub.term_destination    = to_callback_terminate;
+              to_callback_destmgr.error = error;
+              to_callback_destmgr.save_func = save_func;
+              to_callback_destmgr.user_data = user_data;
+              cinfo.dest = (struct jpeg_destination_mgr*) &to_callback_destmgr;
+       } else {
+              jpeg_stdio_dest (&cinfo, f);
+       }
        cinfo.image_width      = w;
        cinfo.image_height     = h;
        cinfo.input_components = 3; 
@@ -895,7 +1230,7 @@ gdk_pixbuf__jpeg_image_save (FILE          *f,
        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);
+                       memcpy (&(buf[j*3]), &(ptr[i*rowstride + j*n_channels]), 3);
 
                /* write scanline */
                jbuf = (JSAMPROW *)(&buf);
@@ -909,21 +1244,50 @@ gdk_pixbuf__jpeg_image_save (FILE          *f,
        jpeg_finish_compress (&cinfo);
        jpeg_destroy_compress(&cinfo);
        g_free (buf);
+       g_free (to_callback_destmgr.buffer);
        return TRUE;
 }
 
-void
-MODULE_ENTRY (jpeg, fill_vtable) (GdkPixbufModule *module)
+static gboolean
+gdk_pixbuf__jpeg_image_save (FILE          *f, 
+                             GdkPixbuf     *pixbuf, 
+                             gchar        **keys,
+                             gchar        **values,
+                             GError       **error)
+{
+       return real_save_jpeg (pixbuf, keys, values, error,
+                              FALSE, f, NULL, NULL);
+}
+
+static gboolean
+gdk_pixbuf__jpeg_image_save_to_callback (GdkPixbufSaveFunc   save_func,
+                                        gpointer            user_data,
+                                        GdkPixbuf          *pixbuf, 
+                                        gchar             **keys,
+                                        gchar             **values,
+                                        GError            **error)
+{
+       return real_save_jpeg (pixbuf, keys, values, error,
+                              TRUE, NULL, save_func, user_data);
+}
+
+#ifndef INCLUDE_jpeg
+#define MODULE_ENTRY(function) G_MODULE_EXPORT void function
+#else
+#define MODULE_ENTRY(function) void _gdk_pixbuf__jpeg_ ## function
+#endif
+
+MODULE_ENTRY (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;
+       module->save_to_callback = gdk_pixbuf__jpeg_image_save_to_callback;
 }
 
-void
-MODULE_ENTRY (jpeg, fill_info) (GdkPixbufFormat *info)
+MODULE_ENTRY (fill_info) (GdkPixbufFormat *info)
 {
        static GdkPixbufModulePattern signature[] = {
                { "\xff\xd8", NULL, 100 },
@@ -945,5 +1309,6 @@ MODULE_ENTRY (jpeg, fill_info) (GdkPixbufFormat *info)
        info->description = N_("The JPEG image format");
        info->mime_types = mime_types;
        info->extensions = extensions;
-       info->flags = GDK_PIXBUF_FORMAT_WRITABLE;
+       info->flags = GDK_PIXBUF_FORMAT_WRITABLE | GDK_PIXBUF_FORMAT_THREADSAFE;
+       info->license = "LGPL";
 }