Adding upstream version 2.10.36.upstream/2.10.36

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1816 insertions, 0 deletions

diff --git a/libgimpbase/gimpmetadata.c b/libgimpbase/gimpmetadata.c
new file mode 100644
index 0000000..9f4f53b
--- /dev/null
+++ b/libgimpbase/gimpmetadata.c
@@ -0,0 +1,1816 @@
+/* LIBGIMPBASE - The GIMP Basic Library
+ * Copyright (C) 1995-1997 Peter Mattis and Spencer Kimball
+ *
+ * gimpmetadata.c
+ * Copyright (C) 2013 Hartmut Kuhse <hartmutkuhse@src.gnome.org>
+ *                    Michael Natterer <mitch@gimp.org>
+ *
+ * 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 3 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, see
+ * <https://www.gnu.org/licenses/>.
+ */
+
+#include "config.h"
+
+#include <stdlib.h>
+#include <string.h>
+
+#include <gio/gio.h>
+#include <gexiv2/gexiv2.h>
+
+#include "libgimpmath/gimpmath.h"
+
+#include "gimpbasetypes.h"
+
+#include "gimplimits.h"
+#include "gimpmetadata.h"
+#include "gimpunit.h"
+
+#include "libgimp/libgimp-intl.h"
+
+typedef struct _GimpMetadataClass   GimpMetadataClass;
+typedef struct _GimpMetadataPrivate GimpMetadataPrivate;
+
+struct _GimpMetadata
+{
+  GExiv2Metadata parent_instance;
+};
+
+struct _GimpMetadataPrivate
+{
+  /* dummy entry to avoid a critical warning due to size 0 */
+  gpointer _gimp_reserved1;
+};
+
+struct _GimpMetadataClass
+{
+  GExiv2MetadataClass parent_class;
+
+  /* Padding for future expansion */
+  void (*_gimp_reserved1) (void);
+  void (*_gimp_reserved2) (void);
+  void (*_gimp_reserved3) (void);
+  void (*_gimp_reserved4) (void);
+  void (*_gimp_reserved5) (void);
+  void (*_gimp_reserved6) (void);
+  void (*_gimp_reserved7) (void);
+  void (*_gimp_reserved8) (void);
+};
+
+/**
+ * SECTION: gimpmetadata
+ * @title: GimpMetadata
+ * @short_description: Basic functions for handling #GimpMetadata objects.
+ * @see_also: gimp_image_metadata_load_prepare(),
+ *            gimp_image_metadata_load_finish(),
+ *            gimp_image_metadata_save_prepare(),
+ *            gimp_image_metadata_save_finish().
+ *
+ * Basic functions for handling #GimpMetadata objects.
+ **/
+
+
+#define GIMP_METADATA_ERROR gimp_metadata_error_quark ()
+
+static GQuark   gimp_metadata_error_quark (void);
+static void     gimp_metadata_copy_tag    (GExiv2Metadata  *src,
+                                           GExiv2Metadata  *dest,
+                                           const gchar     *tag);
+static void     gimp_metadata_copy_tags   (GExiv2Metadata  *src,
+                                           GExiv2Metadata  *dest,
+                                           const gchar    **tags);
+static void     gimp_metadata_add         (GimpMetadata    *src,
+                                           GimpMetadata    *dest);
+
+
+static const gchar *tiff_tags[] =
+{
+  "Xmp.tiff",
+  "Exif.Image.ImageWidth",
+  "Exif.Image.ImageLength",
+  "Exif.Image.BitsPerSample",
+  "Exif.Image.Compression",
+  "Exif.Image.PhotometricInterpretation",
+  "Exif.Image.FillOrder",
+  "Exif.Image.SamplesPerPixel",
+  "Exif.Image.StripOffsets",
+  "Exif.Image.RowsPerStrip",
+  "Exif.Image.StripByteCounts",
+  "Exif.Image.PlanarConfiguration"
+};
+
+static const gchar *jpeg_tags[] =
+{
+  "Exif.Image.JPEGProc",
+  "Exif.Image.JPEGInterchangeFormat",
+  "Exif.Image.JPEGInterchangeFormatLength",
+  "Exif.Image.JPEGRestartInterval",
+  "Exif.Image.JPEGLosslessPredictors",
+  "Exif.Image.JPEGPointTransforms",
+  "Exif.Image.JPEGQTables",
+  "Exif.Image.JPEGDCTables",
+  "Exif.Image.JPEGACTables"
+};
+
+static const gchar *unsupported_tags[] =
+{
+  "Exif.Image.SubIFDs",
+  "Exif.Image.ClipPath",
+  "Exif.Image.XClipPathUnits",
+  "Exif.Image.YClipPathUnits",
+  "Exif.Image.XPTitle",
+  "Exif.Image.XPComment",
+  "Exif.Image.XPAuthor",
+  "Exif.Image.XPKeywords",
+  "Exif.Image.XPSubject",
+  "Exif.Image.DNGVersion",
+  "Exif.Image.DNGBackwardVersion",
+  "Exif.Iop",
+  /* FIXME Even though adding the tags below fixes the issue it's not very flexible.
+     It might be better in the long run if there was a way for a user to configure which
+     tags to block or a way for us to detect problems with tags before writing them. */
+  /* Issues #1367, #2253. Offending tag is PreviewOffset but the other Preview tags
+     (PreviewResolution, PreviewLength, PreviewImageBorders) also make no sense because
+     we are not including a Pentax specific preview image. */
+  "Exif.Pentax.Preview",
+  "Exif.PentaxDng.Preview",
+  /* Never save the complete brand specific MakerNote data. We load and
+   * should only save the specific brand tags inside the MakerNote.
+   * Sometimes the MakerNote is invalid or exiv2 doesn't know how to parse
+   * it. In that case we still get the (invalid) MakerNote, but not the
+   * individual tags or just a subset of them.
+   * If there are recognized brand specific tags, exiv2 will create the
+   * required MakerNote itself (which in can still be invalid but that's an
+   * exiv2 issue not ours). */
+  "Exif.Photo.MakerNote",
+  "Exif.MakerNote.ByteOrder",
+  "Exif.MakerNote.Offset",
+  /* Photoshop resources can contain sensitive data. We should not save the
+   * unedited original state. */
+  "Exif.Image.ImageResources",
+  "Exif.Image.0x935c",
+};
+
+static const guint8 minimal_exif[] =
+{
+  0xff, 0xd8, 0xff, 0xe0, 0x00, 0x10, 0x4a, 0x46, 0x49, 0x46, 0x00, 0x01,
+  0x01, 0x01, 0x00, 0x5a, 0x00, 0x5a, 0x00, 0x00, 0xff, 0xe1
+};
+
+static const guint8 wilber_jpg[] =
+{
+  0xff, 0xd8, 0xff, 0xe0, 0x00, 0x10, 0x4a, 0x46, 0x49, 0x46, 0x00, 0x01,
+  0x01, 0x01, 0x00, 0x5a, 0x00, 0x5a, 0x00, 0x00, 0xff, 0xdb, 0x00, 0x43,
+  0x00, 0x50, 0x37, 0x3c, 0x46, 0x3c, 0x32, 0x50, 0x46, 0x41, 0x46, 0x5a,
+  0x55, 0x50, 0x5f, 0x78, 0xc8, 0x82, 0x78, 0x6e, 0x6e, 0x78, 0xf5, 0xaf,
+  0xb9, 0x91, 0xc8, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xdb, 0x00, 0x43, 0x01, 0x55, 0x5a,
+  0x5a, 0x78, 0x69, 0x78, 0xeb, 0x82, 0x82, 0xeb, 0xff, 0xff, 0xff, 0xff,
+  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+  0xff, 0xff, 0xff, 0xc0, 0x00, 0x11, 0x08, 0x00, 0x10, 0x00, 0x10, 0x03,
+  0x01, 0x22, 0x00, 0x02, 0x11, 0x01, 0x03, 0x11, 0x01, 0xff, 0xc4, 0x00,
+  0x16, 0x00, 0x01, 0x01, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x03, 0x01, 0x02, 0xff, 0xc4, 0x00,
+  0x1e, 0x10, 0x00, 0x01, 0x05, 0x00, 0x02, 0x03, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x02, 0x03, 0x11, 0x31,
+  0x04, 0x12, 0x51, 0x61, 0x71, 0xff, 0xc4, 0x00, 0x14, 0x01, 0x01, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0xff, 0xc4, 0x00, 0x14, 0x11, 0x01, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0xff, 0xda, 0x00, 0x0c, 0x03, 0x01, 0x00, 0x02, 0x11, 0x03, 0x11,
+  0x00, 0x3f, 0x00, 0x18, 0xa0, 0x0e, 0x6d, 0xbc, 0xf5, 0xca, 0xf7, 0x78,
+  0xb6, 0xfe, 0x3b, 0x23, 0xb2, 0x1d, 0x64, 0x68, 0xf0, 0x8a, 0x39, 0x4b,
+  0x74, 0x9c, 0xa5, 0x5f, 0x35, 0x8a, 0xb2, 0x7e, 0xa0, 0xff, 0xd9, 0x00
+};
+
+static const guint wilber_jpg_len = G_N_ELEMENTS (wilber_jpg);
+
+G_DEFINE_TYPE_WITH_PRIVATE (GimpMetadata, gimp_metadata, GEXIV2_TYPE_METADATA)
+
+
+static void
+gimp_metadata_class_init (GimpMetadataClass *klass)
+{
+  if (! gexiv2_metadata_register_xmp_namespace ("http://ns.adobe.com/DICOM/",
+                                                "DICOM"))
+    {
+      g_printerr ("Failed to register XMP namespace 'DICOM'\n");
+    }
+
+  if (! gexiv2_metadata_register_xmp_namespace ("http://darktable.sf.net/",
+                                                "darktable"))
+    {
+      g_printerr ("Failed to register XMP namespace 'darktable'\n");
+    }
+
+  /* Usage example Xmp.GIMP.tagname */
+  if (! gexiv2_metadata_register_xmp_namespace ("http://www.gimp.org/xmp/",
+                                                "GIMP"))
+    {
+      g_printerr ("Failed to register XMP namespace 'GIMP'\n");
+    }
+}
+
+static void
+gimp_metadata_init (GimpMetadata *metadata)
+{
+}
+
+/**
+ * gimp_metadata_get_guid:
+ *
+ * Generate Version 4 UUID/GUID.
+ *
+ * Return value: The new GUID/UUID string.
+ *
+ * Since: 2.10
+ */
+gchar *
+gimp_metadata_get_guid (void)
+{
+  GRand       *rand;
+  gint         bake;
+  gchar       *GUID;
+  const gchar *szHex = "0123456789abcdef-";
+
+  rand = g_rand_new ();
+
+#define DALLOC 36
+
+  GUID = g_malloc0 (DALLOC + 1);
+
+  for (bake = 0; bake < DALLOC; bake++)
+    {
+      gint  r = g_rand_int (rand) % 16;
+      gchar c = ' ';
+
+      switch (bake)
+        {
+        default:
+          c = szHex [r];
+          break;
+
+        case 19 :
+          c = szHex [(r & 0x03) | 0x08];
+          break;
+
+        case 8:
+        case 13:
+        case 18:
+        case 23:
+          c = '-';
+          break;
+
+        case 14:
+          c = '4';
+          break;
+        }
+
+      GUID[bake] = (bake < DALLOC) ? c : 0x00;
+    }
+
+  g_rand_free (rand);
+
+  return GUID;
+}
+
+/**
+ * gimp_metadata_add_history:
+ *
+ * Add XMP mm History data to file metadata.
+ *
+ * Since: 2.10
+ */
+void
+gimp_metadata_add_xmp_history (GimpMetadata *metadata,
+                               gchar        *state_status)
+{
+  time_t     now;
+  struct tm *now_tm;
+  gchar     *tmp;
+  char       timestr[256];
+  char       tzstr[7];
+  gchar      iid_data[256];
+  gchar      strdata[1024];
+  gchar      tagstr[1024];
+  gchar     *uuid;
+  gchar     *did;
+  gchar     *odid;
+  gint       id_count;
+  gint       found;
+  gint       lastfound;
+  gint       count;
+  int        ii;
+
+  static const gchar *tags[] =
+  {
+    "Xmp.xmpMM.InstanceID",
+    "Xmp.xmpMM.DocumentID",
+    "Xmp.xmpMM.OriginalDocumentID",
+    "Xmp.xmpMM.History"
+  };
+
+  static const gchar *history_tags[] =
+  {
+    "/stEvt:action",
+    "/stEvt:instanceID",
+    "/stEvt:when",
+    "/stEvt:softwareAgent",
+    "/stEvt:changed"
+  };
+
+  g_return_if_fail (GIMP_IS_METADATA (metadata));
+
+  /* Update new Instance ID */
+  uuid = gimp_metadata_get_guid ();
+
+  strcpy (iid_data, "xmp.iid:");
+  strcat (iid_data, uuid);
+
+  gexiv2_metadata_set_tag_string (GEXIV2_METADATA (metadata),
+                                  tags[0], iid_data);
+  g_free (uuid);
+
+  /* Update new Document ID if none found */
+  did = gexiv2_metadata_get_tag_interpreted_string (GEXIV2_METADATA (metadata),
+                                                    tags[1]);
+  if (! did || ! strlen (did))
+    {
+      gchar did_data[256];
+
+      uuid = gimp_metadata_get_guid ();
+
+      strcpy (did_data, "gimp:docid:gimp:");
+      strcat (did_data, uuid);
+
+      gexiv2_metadata_set_tag_string (GEXIV2_METADATA (metadata),
+                                      tags[1], did_data);
+      g_free (uuid);
+    }
+
+  /* Update new Original Document ID if none found */
+  odid = gexiv2_metadata_get_tag_interpreted_string (GEXIV2_METADATA (metadata),
+                                                     tags[2]);
+  if (! odid || ! strlen (odid))
+    {
+      gchar  did_data[256];
+      gchar *uuid = gimp_metadata_get_guid ();
+
+      strcpy (did_data, "xmp.did:");
+      strcat (did_data, uuid);
+
+      gexiv2_metadata_set_tag_string (GEXIV2_METADATA (metadata),
+                                      tags[2], did_data);
+      g_free (uuid);
+    }
+
+  /* Handle Xmp.xmpMM.History */
+
+  gexiv2_metadata_set_xmp_tag_struct (GEXIV2_METADATA (metadata),
+                                      tags[3],
+                                      GEXIV2_STRUCTURE_XA_SEQ);
+
+  /* Find current number of entries for Xmp.xmpMM.History */
+  found = 0;
+  for (count = 1; count < 65536; count++)
+    {
+      lastfound = 0;
+      for (ii = 0; ii < 5; ii++)
+        {
+          g_snprintf (tagstr, sizeof (tagstr), "%s[%d]%s",
+                      tags[3], count, history_tags[ii]);
+
+          if (gexiv2_metadata_has_tag (GEXIV2_METADATA (metadata),
+                                       tagstr))
+            {
+              lastfound = 1;
+            }
+        }
+
+      if (lastfound == 0)
+        break;
+
+      found++;
+    }
+
+  id_count = found + 1;
+
+  memset (tagstr, 0, sizeof (tagstr));
+  memset (strdata, 0, sizeof (strdata));
+
+  g_snprintf (tagstr, sizeof (tagstr), "%s[%d]%s",
+              tags[3], id_count, history_tags[0]);
+
+  gexiv2_metadata_set_tag_string (GEXIV2_METADATA (metadata),
+                                  tagstr, "saved");
+
+  memset (tagstr, 0, sizeof (tagstr));
+  memset (strdata, 0, sizeof (strdata));
+
+  uuid = gimp_metadata_get_guid ();
+
+  g_snprintf (tagstr, sizeof (tagstr), "%s[%d]%s",
+              tags[3], id_count, history_tags[1]);
+  g_snprintf (strdata, sizeof (strdata), "xmp.iid:%s",
+              uuid);
+
+  gexiv2_metadata_set_tag_string (GEXIV2_METADATA (metadata),
+                                  tagstr, strdata);
+  g_free(uuid);
+
+  memset (tagstr, 0, sizeof (tagstr));
+  memset (strdata, 0, sizeof (strdata));
+
+  g_snprintf (tagstr, sizeof (tagstr), "%s[%d]%s",
+              tags[3], id_count, history_tags[2]);
+
+  /* get local time */
+  time (&now);
+  now_tm = localtime (&now);
+
+  /* get timezone and fix format */
+  strftime (tzstr, 7, "%z", now_tm);
+  tzstr[6] = '\0';
+  tzstr[5] = tzstr[4];
+  tzstr[4] = tzstr[3];
+  tzstr[3] = ':';
+
+  /* get current time and timezone string */
+  strftime (timestr, 256, "%Y-%m-%dT%H:%M:%S", now_tm);
+  tmp = g_strdup_printf ("%s%s", timestr, tzstr);
+  gexiv2_metadata_set_tag_string (GEXIV2_METADATA (metadata),
+                                  tagstr, tmp);
+  g_free (tmp);
+
+  memset (tagstr, 0, sizeof (tagstr));
+  memset (strdata, 0, sizeof (strdata));
+
+  g_snprintf (tagstr, sizeof (tagstr), "%s[%d]%s",
+              tags[3], id_count, history_tags[3]);
+
+  gexiv2_metadata_set_tag_string (GEXIV2_METADATA (metadata),
+                                  tagstr,
+                                  "Gimp 2.10 "
+#if defined(_WIN32) || defined(__CYGWIN__) || defined(__MINGW32__)
+                                  "(Windows)");
+#elif defined(__linux__)
+                                  "(Linux)");
+#elif defined(__APPLE__) && defined(__MACH__)
+                                  "(Mac OS)");
+#elif defined(unix) || defined(__unix__) || defined(__unix)
+                                  "(Unix)");
+#else
+                                  "(Unknown)");
+#endif
+
+  memset (tagstr, 0, sizeof (tagstr));
+  memset (strdata, 0, sizeof (strdata));
+
+  g_snprintf (tagstr, sizeof (tagstr), "%s[%d]%s",
+              tags[3], id_count, history_tags[4]);
+
+  strcpy (strdata, "/");
+  strcat (strdata, state_status);
+
+  gexiv2_metadata_set_tag_string (GEXIV2_METADATA (metadata),
+                                  tagstr, strdata);
+}
+
+/**
+ * gimp_metadata_new:
+ *
+ * Creates a new #GimpMetadata instance.
+ *
+ * Return value: The new #GimpMetadata.
+ *
+ * Since: 2.10
+ */
+GimpMetadata *
+gimp_metadata_new (void)
+{
+  GimpMetadata *metadata = NULL;
+
+  if (gexiv2_initialize ())
+    {
+      metadata = g_object_new (GIMP_TYPE_METADATA, NULL);
+
+      if (! gexiv2_metadata_open_buf (GEXIV2_METADATA (metadata),
+                                      wilber_jpg, wilber_jpg_len,
+                                      NULL))
+        {
+          g_object_unref (metadata);
+
+          return NULL;
+        }
+    }
+
+  return metadata;
+}
+
+/**
+ * gimp_metadata_duplicate:
+ * @metadata: The object to duplicate, or %NULL.
+ *
+ * Duplicates a #GimpMetadata instance.
+ *
+ * Return value: The new #GimpMetadata, or %NULL if @metadata is %NULL.
+ *
+ * Since: 2.10
+ */
+GimpMetadata *
+gimp_metadata_duplicate (GimpMetadata *metadata)
+{
+  GimpMetadata *new_metadata = NULL;
+
+  g_return_val_if_fail (metadata == NULL || GIMP_IS_METADATA (metadata), NULL);
+
+  if (metadata)
+    {
+      gchar *xml;
+
+      xml = gimp_metadata_serialize (metadata);
+      new_metadata = gimp_metadata_deserialize (xml);
+      g_free (xml);
+    }
+
+  return new_metadata;
+}
+
+typedef struct
+{
+  gchar         name[1024];
+  gboolean      base64;
+  gboolean      excessive_message_shown;
+  GimpMetadata *metadata;
+} GimpMetadataParseData;
+
+static const gchar*
+gimp_metadata_attribute_name_to_value (const gchar **attribute_names,
+                                       const gchar **attribute_values,
+                                       const gchar  *name)
+{
+  while (*attribute_names)
+    {
+      if (! strcmp (*attribute_names, name))
+        {
+          return *attribute_values;
+        }
+
+      attribute_names++;
+      attribute_values++;
+    }
+
+  return NULL;
+}
+
+static void
+gimp_metadata_deserialize_start_element (GMarkupParseContext *context,
+                                         const gchar         *element_name,
+                                         const gchar        **attribute_names,
+                                         const gchar        **attribute_values,
+                                         gpointer             user_data,
+                                         GError             **error)
+{
+  GimpMetadataParseData *parse_data = user_data;
+
+  if (! strcmp (element_name, "tag"))
+    {
+      const gchar *name;
+      const gchar *encoding;
+
+      name = gimp_metadata_attribute_name_to_value (attribute_names,
+                                                    attribute_values,
+                                                    "name");
+      encoding = gimp_metadata_attribute_name_to_value (attribute_names,
+                                                        attribute_values,
+                                                        "encoding");
+
+      if (! name)
+        {
+          g_set_error (error, GIMP_METADATA_ERROR, 1001,
+                       "Element 'tag' does not contain required attribute 'name'.");
+          return;
+        }
+
+      strncpy (parse_data->name, name, sizeof (parse_data->name));
+      parse_data->name[sizeof (parse_data->name) - 1] = 0;
+
+      parse_data->base64 = (encoding && ! strcmp (encoding, "base64"));
+    }
+}
+
+static void
+gimp_metadata_deserialize_end_element (GMarkupParseContext *context,
+                                       const gchar         *element_name,
+                                       gpointer             user_data,
+                                       GError             **error)
+{
+}
+
+static void
+gimp_metadata_deserialize_text (GMarkupParseContext  *context,
+                                const gchar          *text,
+                                gsize                 text_len,
+                                gpointer              user_data,
+                                GError              **error)
+{
+  GimpMetadataParseData *parse_data = user_data;
+  const gchar           *current_element;
+
+  current_element = g_markup_parse_context_get_element (context);
+
+  if (! g_strcmp0 (current_element, "tag"))
+    {
+      gchar *value = g_strndup (text, text_len);
+
+      if (parse_data->base64)
+        {
+          guchar *decoded;
+          gsize   len;
+
+          decoded = g_base64_decode (value, &len);
+
+          if (decoded[len - 1] == '\0')
+            {
+              g_free (value);
+              value = (gchar *) decoded;
+            }
+          else
+            {
+              g_clear_pointer (&value,   g_free);
+              g_clear_pointer (&decoded, g_free);
+            }
+        }
+
+      if (value)
+        {
+          GExiv2Metadata  *g2_metadata = GEXIV2_METADATA (parse_data->metadata);
+          gchar          **values;
+
+          values = gexiv2_metadata_get_tag_multiple (g2_metadata,
+                                                     parse_data->name);
+
+          if (values)
+            {
+              guint length = g_strv_length (values);
+
+              if (length > 1000 &&
+                  ! g_strcmp0 (parse_data->name, "Xmp.photoshop.DocumentAncestors"))
+                {
+                  /* Issue #8025, see also #7464 Some XCF images can have huge
+                   * amounts of this tag, apparently due to a bug in PhotoShop.
+                   * This makes deserializing it in the way we currently do
+                   * too slow. Until we can change this let's ignore everything
+                   * but the first 1000 values when serializing. */
+
+                  if (! parse_data->excessive_message_shown)
+                    {
+                      g_message ("Excessive number of Xmp.photoshop.DocumentAncestors tags found. "
+                                 "Only keeping the first 1000 values.");
+                      parse_data->excessive_message_shown = TRUE;
+                    }
+                }
+              else
+                {
+                  values = g_renew (gchar *, values, length + 2);
+                  values[length]     = value;
+                  values[length + 1] = NULL;
+
+                  gexiv2_metadata_set_tag_multiple (g2_metadata,
+                                                    parse_data->name,
+                                                    (const gchar **) values);
+                }
+              g_strfreev (values);
+            }
+          else
+            {
+              gexiv2_metadata_set_tag_string (GEXIV2_METADATA (g2_metadata),
+                                              parse_data->name,
+                                              value);
+              g_free (value);
+            }
+        }
+    }
+}
+
+static  void
+gimp_metadata_deserialize_error (GMarkupParseContext *context,
+                                 GError              *error,
+                                 gpointer             user_data)
+{
+  g_printerr ("Metadata parse error: %s\n", error->message);
+}
+
+/**
+ * gimp_metadata_deserialize:
+ * @metadata_xml: A string of serialized metadata XML.
+ *
+ * Deserializes a string of XML that has been created by
+ * gimp_metadata_serialize().
+ *
+ * Return value: The new #GimpMetadata.
+ *
+ * Since: 2.10
+ */
+GimpMetadata *
+gimp_metadata_deserialize (const gchar *metadata_xml)
+{
+  GimpMetadata          *metadata;
+  GMarkupParser          markup_parser;
+  GimpMetadataParseData  parse_data;
+  GMarkupParseContext   *context;
+
+  g_return_val_if_fail (metadata_xml != NULL, NULL);
+
+  metadata = gimp_metadata_new ();
+
+  parse_data.metadata = metadata;
+  parse_data.excessive_message_shown = FALSE;
+
+  markup_parser.start_element = gimp_metadata_deserialize_start_element;
+  markup_parser.end_element   = gimp_metadata_deserialize_end_element;
+  markup_parser.text          = gimp_metadata_deserialize_text;
+  markup_parser.passthrough   = NULL;
+  markup_parser.error         = gimp_metadata_deserialize_error;
+
+  context = g_markup_parse_context_new (&markup_parser, 0, &parse_data, NULL);
+
+  g_markup_parse_context_parse (context,
+                                metadata_xml, strlen (metadata_xml),
+                                NULL);
+
+  g_markup_parse_context_unref (context);
+
+  return metadata;
+}
+
+static gchar *
+gimp_metadata_escape (const gchar *name,
+                      const gchar *value,
+                      gboolean    *base64)
+{
+  if (! g_utf8_validate (value, -1, NULL))
+    {
+      gchar *encoded;
+
+      encoded = g_base64_encode ((const guchar *) value, strlen (value) + 1);
+
+      g_printerr ("Invalid UTF-8 in metadata value %s, encoding as base64: %s\n",
+                  name, encoded);
+
+      *base64 = TRUE;
+
+      return encoded;
+    }
+
+  *base64 = FALSE;
+
+  return g_markup_escape_text (value, -1);
+}
+
+static void
+gimp_metadata_append_tag (GString     *string,
+                          const gchar *name,
+                          gchar       *value,
+                          gboolean     base64)
+{
+  if (value)
+    {
+      if (base64)
+        {
+          g_string_append_printf (string, "  <tag name=\"%s\" encoding=\"base64\">%s</tag>\n",
+                                  name, value);
+        }
+      else
+        {
+          g_string_append_printf (string, "  <tag name=\"%s\">%s</tag>\n",
+                                  name, value);
+        }
+
+      g_free (value);
+    }
+}
+
+/**
+ * gimp_metadata_serialize:
+ * @metadata: A #GimpMetadata instance.
+ *
+ * Serializes @metadata into an XML string that can later be deserialized
+ * using gimp_metadata_deserialize().
+ *
+ * Return value: The serialized XML string.
+ *
+ * Since: 2.10
+ */
+gchar *
+gimp_metadata_serialize (GimpMetadata *metadata)
+{
+  GString  *string;
+  gchar   **exif_data = NULL;
+  gchar   **iptc_data = NULL;
+  gchar   **xmp_data  = NULL;
+  gchar    *value;
+  gchar    *escaped;
+  gboolean  base64;
+  gint      i;
+
+  g_return_val_if_fail (GIMP_IS_METADATA (metadata), NULL);
+
+  string = g_string_new (NULL);
+
+  g_string_append (string, "<?xml version='1.0' encoding='UTF-8'?>\n");
+  g_string_append (string, "<metadata>\n");
+
+  exif_data = gexiv2_metadata_get_exif_tags (GEXIV2_METADATA (metadata));
+
+  if (exif_data)
+    {
+      for (i = 0; exif_data[i] != NULL; i++)
+        {
+          value = gexiv2_metadata_get_tag_string (GEXIV2_METADATA (metadata),
+                                                  exif_data[i]);
+          escaped = gimp_metadata_escape (exif_data[i], value, &base64);
+          g_free (value);
+
+          gimp_metadata_append_tag (string, exif_data[i], escaped, base64);
+        }
+
+      g_strfreev (exif_data);
+    }
+
+  xmp_data = gexiv2_metadata_get_xmp_tags (GEXIV2_METADATA (metadata));
+
+  if (xmp_data)
+    {
+      for (i = 0; xmp_data[i] != NULL; i++)
+        {
+          /* XmpText is always a single value, but structures like
+           * XmpBag and XmpSeq can have multiple values that need to be
+           * treated separately or else saving will do things wrong. */
+          if (! g_strcmp0 (gexiv2_metadata_get_tag_type (xmp_data[i]), "XmpText"))
+            {
+              value = gexiv2_metadata_get_tag_string (GEXIV2_METADATA (metadata),
+                                                      xmp_data[i]);
+              escaped = gimp_metadata_escape (xmp_data[i], value, &base64);
+              g_free (value);
+
+              gimp_metadata_append_tag (string, xmp_data[i], escaped, base64);
+            }
+          else
+            {
+              gchar **values;
+
+              values = gexiv2_metadata_get_tag_multiple (GEXIV2_METADATA (metadata),
+                                                         xmp_data[i]);
+
+              if (values)
+                {
+                  gint  vi;
+                  gint  cnt = 0;
+
+                  if (! g_strcmp0 (xmp_data[i], "Xmp.photoshop.DocumentAncestors"))
+                    {
+                      /* Issue #7464 Some images can have huge amounts of this
+                       * tag (more than 100000 in certain cases), apparently
+                       * due to a bug in PhotoShop. This makes deserializing it
+                       * in the way we currently do too slow. Until we can
+                       * change this let's remove everything but the first 1000
+                       * values when serializing. */
+                      cnt = g_strv_length (values);
+
+                      if (cnt > 1000)
+                        {
+                          g_message ("Excessive number of Xmp.photoshop.DocumentAncestors tags found: %d. "
+                                     "Only keeping the first 1000 values.", cnt);
+                        }
+                    }
+
+                  for (vi = 0; values[vi] != NULL && (cnt <= 1000 || vi < 1000); vi++)
+                    {
+                      escaped = gimp_metadata_escape (xmp_data[i], values[vi], &base64);
+                      gimp_metadata_append_tag (string, xmp_data[i], escaped, base64);
+                    }
+
+                  g_strfreev (values);
+                }
+            }
+        }
+      g_strfreev (xmp_data);
+    }
+
+  iptc_data = gexiv2_metadata_get_iptc_tags (GEXIV2_METADATA (metadata));
+
+  if (iptc_data)
+    {
+      gchar **iptc_tags = iptc_data;
+      gchar  *last_tag  = NULL;
+
+      while (*iptc_tags)
+        {
+          gchar **values;
+
+          if (last_tag && ! strcmp (*iptc_tags, last_tag))
+            {
+              iptc_tags++;
+              continue;
+            }
+          last_tag = *iptc_tags;
+
+          values = gexiv2_metadata_get_tag_multiple (GEXIV2_METADATA (metadata),
+                                                     *iptc_tags);
+
+          if (values)
+            {
+              for (i = 0; values[i] != NULL; i++)
+                {
+                  escaped = gimp_metadata_escape (*iptc_tags, values[i], &base64);
+                  gimp_metadata_append_tag (string, *iptc_tags, escaped, base64);
+                }
+
+              g_strfreev (values);
+            }
+
+          iptc_tags++;
+        }
+
+      g_strfreev (iptc_data);
+    }
+
+  g_string_append (string, "</metadata>\n");
+
+  return g_string_free (string, FALSE);
+}
+
+/**
+ * gimp_metadata_load_from_file:
+ * @file:  The #GFile to load the metadata from
+ * @error: Return location for error message
+ *
+ * Loads #GimpMetadata from @file.
+ *
+ * Return value: The loaded #GimpMetadata.
+ *
+ * Since: 2.10
+ */
+GimpMetadata  *
+gimp_metadata_load_from_file (GFile   *file,
+                              GError **error)
+{
+  GimpMetadata *meta = NULL;
+  gchar        *path;
+  gchar        *filename;
+
+  g_return_val_if_fail (G_IS_FILE (file), NULL);
+  g_return_val_if_fail (error == NULL || *error == NULL, NULL);
+
+  path = g_file_get_path (file);
+
+  if (! path)
+    {
+      g_set_error (error, GIMP_METADATA_ERROR, 0,
+                   _("Can load metadata only from local files"));
+      return NULL;
+    }
+
+  filename = g_strdup (path);
+
+  g_free (path);
+
+  if (gexiv2_initialize ())
+    {
+      meta = g_object_new (GIMP_TYPE_METADATA, NULL);
+
+      if (! gexiv2_metadata_open_path (GEXIV2_METADATA (meta), filename, error))
+        {
+          g_object_unref (meta);
+          g_free (filename);
+
+          return NULL;
+        }
+    }
+
+  g_free (filename);
+
+  return meta;
+}
+
+/**
+ * gimp_metadata_save_to_file:
+ * @metadata: A #GimpMetadata instance.
+ * @file:     The file to save the metadata to
+ * @error:    Return location for error message
+ *
+ * Saves @metadata to @file.
+ *
+ * Return value: %TRUE on success, %FALSE otherwise.
+ *
+ * Since: 2.10
+ */
+gboolean
+gimp_metadata_save_to_file (GimpMetadata  *metadata,
+                            GFile         *file,
+                            GError       **error)
+{
+  gchar    *path;
+  gchar    *filename;
+  gboolean  success;
+
+  g_return_val_if_fail (GIMP_IS_METADATA (metadata), FALSE);
+  g_return_val_if_fail (G_IS_FILE (file), FALSE);
+  g_return_val_if_fail (error == NULL || *error == NULL, FALSE);
+
+  path = g_file_get_path (file);
+
+  if (! path)
+    {
+      g_set_error (error, GIMP_METADATA_ERROR, 0,
+                   _("Can save metadata only to local files"));
+      return FALSE;
+    }
+
+  filename = g_strdup (path);
+
+  g_free (path);
+
+  success = gexiv2_metadata_save_file (GEXIV2_METADATA (metadata),
+                                       filename, error);
+
+  g_free (filename);
+
+  return success;
+}
+
+/**
+ * gimp_metadata_set_from_exif:
+ * @metadata:         A #GimpMetadata instance.
+ * @exif_data:        The blob of Exif data to set
+ * @exif_data_length: Length of @exif_data, in bytes
+ * @error:            Return location for error message
+ *
+ * Sets the tags from a piece of Exif data on @metadata.
+ *
+ * Return value: %TRUE on success, %FALSE otherwise.
+ *
+ * Since: 2.10
+ */
+gboolean
+gimp_metadata_set_from_exif (GimpMetadata  *metadata,
+                             const guchar  *exif_data,
+                             gint           exif_data_length,
+                             GError       **error)
+{
+
+  GByteArray   *exif_bytes;
+  GimpMetadata *exif_metadata;
+  guint8        data_size[2] = { 0, };
+  const guint8  eoi[2] = { 0xff, 0xd9 };
+
+  g_return_val_if_fail (GIMP_IS_METADATA (metadata), FALSE);
+  g_return_val_if_fail (exif_data != NULL || exif_data_length == 0, FALSE);
+  g_return_val_if_fail (error == NULL || *error == NULL, FALSE);
+
+  if (exif_data_length < 0 || exif_data_length + 2 >= 65536)
+    {
+      g_set_error (error, GIMP_METADATA_ERROR, 0,
+                   _("Invalid Exif data size."));
+      return FALSE;
+    }
+
+  data_size[0] = ((exif_data_length + 2) & 0xFF00) >> 8;
+  data_size[1] = ((exif_data_length + 2) & 0x00FF);
+
+  exif_bytes = g_byte_array_new ();
+  exif_bytes = g_byte_array_append (exif_bytes,
+                                    minimal_exif, G_N_ELEMENTS (minimal_exif));
+  exif_bytes = g_byte_array_append (exif_bytes,
+                                    data_size, 2);
+  exif_bytes = g_byte_array_append (exif_bytes,
+                                    (guint8 *) exif_data, exif_data_length);
+  exif_bytes = g_byte_array_append (exif_bytes, eoi, 2);
+
+  exif_metadata = gimp_metadata_new ();
+
+  if (! gexiv2_metadata_open_buf (GEXIV2_METADATA (exif_metadata),
+                                  exif_bytes->data, exif_bytes->len, error))
+    {
+      g_object_unref (exif_metadata);
+      g_byte_array_free (exif_bytes, TRUE);
+      return FALSE;
+    }
+
+  if (! gexiv2_metadata_has_exif (GEXIV2_METADATA (exif_metadata)))
+    {
+      g_set_error (error, GIMP_METADATA_ERROR, 0,
+                   _("Parsing Exif data failed."));
+      g_object_unref (exif_metadata);
+      g_byte_array_free (exif_bytes, TRUE);
+      return FALSE;
+    }
+
+  gimp_metadata_add (exif_metadata, metadata);
+  g_object_unref (exif_metadata);
+  g_byte_array_free (exif_bytes, TRUE);
+
+  return TRUE;
+}
+
+/**
+ * gimp_metadata_set_from_iptc:
+ * @metadata:        A #GimpMetadata instance.
+ * @iptc_data:       The blob of Ipc data to set
+ * @iptc_data_length:Length of @iptc_data, in bytes
+ * @error:           Return location for error message
+ *
+ * Sets the tags from a piece of IPTC data on @metadata.
+ *
+ * Return value: %TRUE on success, %FALSE otherwise.
+ *
+ * Since: 2.10
+ */
+gboolean
+gimp_metadata_set_from_iptc (GimpMetadata  *metadata,
+                             const guchar  *iptc_data,
+                             gint           iptc_data_length,
+                             GError       **error)
+{
+  GimpMetadata *iptc_metadata;
+
+  g_return_val_if_fail (GIMP_IS_METADATA (metadata), FALSE);
+  g_return_val_if_fail (iptc_data != NULL || iptc_data_length == 0, FALSE);
+  g_return_val_if_fail (error == NULL || *error == NULL, FALSE);
+
+  iptc_metadata = gimp_metadata_new ();
+
+  if (! gexiv2_metadata_open_buf (GEXIV2_METADATA (iptc_metadata),
+                                  iptc_data, iptc_data_length, error))
+    {
+      g_object_unref (iptc_metadata);
+      return FALSE;
+    }
+
+  if (! gexiv2_metadata_has_iptc (GEXIV2_METADATA (iptc_metadata)))
+    {
+      g_set_error (error, GIMP_METADATA_ERROR, 0,
+                   _("Parsing IPTC data failed."));
+      g_object_unref (iptc_metadata);
+      return FALSE;
+    }
+
+  gimp_metadata_add (iptc_metadata, metadata);
+  g_object_unref (iptc_metadata);
+
+  return TRUE;
+}
+
+/**
+ * gimp_metadata_set_from_xmp:
+ * @metadata:        A #GimpMetadata instance.
+ * @xmp_data:        The blob of Exif data to set
+ * @xmp_data_length: Length of @exif_data, in bytes
+ * @error:           Return location for error message
+ *
+ * Sets the tags from a piece of XMP data on @metadata.
+ *
+ * Return value: %TRUE on success, %FALSE otherwise.
+ *
+ * Since: 2.10
+ */
+gboolean
+gimp_metadata_set_from_xmp (GimpMetadata  *metadata,
+                            const guchar  *xmp_data,
+                            gint           xmp_data_length,
+                            GError       **error)
+{
+  GimpMetadata *xmp_metadata;
+
+  g_return_val_if_fail (GIMP_IS_METADATA (metadata), FALSE);
+  g_return_val_if_fail (xmp_data != NULL || xmp_data_length == 0, FALSE);
+  g_return_val_if_fail (error == NULL || *error == NULL, FALSE);
+
+  xmp_metadata = gimp_metadata_new ();
+
+  if (! gexiv2_metadata_open_buf (GEXIV2_METADATA (xmp_metadata),
+                                  xmp_data, xmp_data_length, error))
+    {
+      g_object_unref (xmp_metadata);
+      return FALSE;
+    }
+
+  if (! gexiv2_metadata_has_xmp (GEXIV2_METADATA (xmp_metadata)))
+    {
+      g_set_error (error, GIMP_METADATA_ERROR, 0,
+                   _("Parsing XMP data failed."));
+      g_object_unref (xmp_metadata);
+      return FALSE;
+    }
+
+  gimp_metadata_add (xmp_metadata, metadata);
+  g_object_unref (xmp_metadata);
+
+  return TRUE;
+}
+
+/**
+ * gimp_metadata_set_pixel_size:
+ * @metadata: A #GimpMetadata instance.
+ * @width:    Width in pixels
+ * @height:   Height in pixels
+ *
+ * Sets Exif.Image.ImageWidth and Exif.Image.ImageLength on @metadata.
+ * If already present, also sets Exif.Photo.PixelXDimension and
+ * Exif.Photo.PixelYDimension.
+ *
+ * Since: 2.10
+ */
+void
+gimp_metadata_set_pixel_size (GimpMetadata *metadata,
+                              gint          width,
+                              gint          height)
+{
+  gchar buffer[32];
+
+  g_return_if_fail (GIMP_IS_METADATA (metadata));
+
+  g_snprintf (buffer, sizeof (buffer), "%d", width);
+  gexiv2_metadata_set_tag_string (GEXIV2_METADATA (metadata),
+                                  "Exif.Image.ImageWidth", buffer);
+  if (gexiv2_metadata_has_tag (GEXIV2_METADATA (metadata),
+                               "Exif.Photo.PixelXDimension"))
+    {
+      gexiv2_metadata_set_tag_string (GEXIV2_METADATA (metadata),
+                                      "Exif.Photo.PixelXDimension",
+                                      buffer);
+    }
+
+  g_snprintf (buffer, sizeof (buffer), "%d", height);
+  gexiv2_metadata_set_tag_string (GEXIV2_METADATA (metadata),
+                                  "Exif.Image.ImageLength", buffer);
+  if (gexiv2_metadata_has_tag (GEXIV2_METADATA (metadata),
+                               "Exif.Photo.PixelYDimension"))
+    {
+      gexiv2_metadata_set_tag_string (GEXIV2_METADATA (metadata),
+                                      "Exif.Photo.PixelYDimension",
+                                      buffer);
+    }
+}
+
+/**
+ * gimp_metadata_set_bits_per_sample:
+ * @metadata:        A #GimpMetadata instance.
+ * @bits_per_sample: Bits per pixel, per component
+ *
+ * Sets Exif.Image.BitsPerSample on @metadata.
+ *
+ * Since: 2.10
+ */
+void
+gimp_metadata_set_bits_per_sample (GimpMetadata *metadata,
+                                   gint          bits_per_sample)
+{
+  gchar buffer[32];
+
+  g_return_if_fail (GIMP_IS_METADATA (metadata));
+
+  g_snprintf (buffer, sizeof (buffer), "%d %d %d",
+              bits_per_sample, bits_per_sample, bits_per_sample);
+  gexiv2_metadata_set_tag_string (GEXIV2_METADATA (metadata),
+                                  "Exif.Image.BitsPerSample", buffer);
+}
+
+/**
+ * gimp_metadata_get_resolution:
+ * @metadata: A #GimpMetadata instance.
+ * @xres:     Return location for the X Resolution, in ppi
+ * @yres:     Return location for the Y Resolution, in ppi
+ * @unit:     Return location for the unit unit
+ *
+ * Returns values based on Exif.Image.XResolution,
+ * Exif.Image.YResolution and Exif.Image.ResolutionUnit of @metadata.
+ *
+ * Return value: %TRUE on success, %FALSE otherwise.
+ *
+ * Since: 2.10
+ */
+gboolean
+gimp_metadata_get_resolution (GimpMetadata *metadata,
+                              gdouble      *xres,
+                              gdouble      *yres,
+                              GimpUnit     *unit)
+{
+  gint xnom, xdenom;
+  gint ynom, ydenom;
+
+  g_return_val_if_fail (GIMP_IS_METADATA (metadata), FALSE);
+
+  if (gexiv2_metadata_get_exif_tag_rational (GEXIV2_METADATA (metadata),
+                                             "Exif.Image.XResolution",
+                                             &xnom, &xdenom) &&
+      gexiv2_metadata_get_exif_tag_rational (GEXIV2_METADATA (metadata),
+                                             "Exif.Image.YResolution",
+                                             &ynom, &ydenom))
+    {
+      gchar *un;
+      gint   exif_unit = 2;
+
+      un = gexiv2_metadata_get_tag_string (GEXIV2_METADATA (metadata),
+                                           "Exif.Image.ResolutionUnit");
+      if (un)
+        {
+          exif_unit = atoi (un);
+          g_free (un);
+        }
+
+      if (xnom != 0 && xdenom != 0 &&
+          ynom != 0 && ydenom != 0)
+        {
+          gdouble xresolution = (gdouble) xnom / (gdouble) xdenom;
+          gdouble yresolution = (gdouble) ynom / (gdouble) ydenom;
+
+          if (exif_unit == 3)
+            {
+              xresolution *= 2.54;
+              yresolution *= 2.54;
+            }
+
+         if (xresolution >= GIMP_MIN_RESOLUTION &&
+             xresolution <= GIMP_MAX_RESOLUTION &&
+             yresolution >= GIMP_MIN_RESOLUTION &&
+             yresolution <= GIMP_MAX_RESOLUTION)
+           {
+             if (xres)
+               *xres = xresolution;
+
+             if (yres)
+               *yres = yresolution;
+
+             if (unit)
+               {
+                 if (exif_unit == 3)
+                   *unit = GIMP_UNIT_MM;
+                 else
+                   *unit = GIMP_UNIT_INCH;
+               }
+
+             return TRUE;
+           }
+        }
+    }
+
+  return FALSE;
+}
+
+/**
+ * gimp_metadata_set_resolution:
+ * @metadata: A #GimpMetadata instance.
+ * @xres:     The image's X Resolution, in ppi
+ * @yres:     The image's Y Resolution, in ppi
+ * @unit:     The image's unit
+ *
+ * Sets Exif.Image.XResolution, Exif.Image.YResolution and
+ * Exif.Image.ResolutionUnit of @metadata.
+ *
+ * Since: 2.10
+ */
+void
+gimp_metadata_set_resolution (GimpMetadata *metadata,
+                              gdouble       xres,
+                              gdouble       yres,
+                              GimpUnit      unit)
+{
+  gchar buffer[32];
+  gint  exif_unit;
+  gint  factor;
+
+  g_return_if_fail (GIMP_IS_METADATA (metadata));
+
+  if (gimp_unit_is_metric (unit))
+    {
+      xres /= 2.54;
+      yres /= 2.54;
+
+      exif_unit = 3;
+    }
+  else
+    {
+      exif_unit = 2;
+    }
+
+  for (factor = 1; factor <= 100 /* arbitrary */; factor++)
+    {
+      if (fabs (xres * factor - ROUND (xres * factor)) < 0.01 &&
+          fabs (yres * factor - ROUND (yres * factor)) < 0.01)
+        break;
+    }
+
+  gexiv2_metadata_set_exif_tag_rational (GEXIV2_METADATA (metadata),
+                                         "Exif.Image.XResolution",
+                                         ROUND (xres * factor), factor);
+
+  gexiv2_metadata_set_exif_tag_rational (GEXIV2_METADATA (metadata),
+                                         "Exif.Image.YResolution",
+                                         ROUND (yres * factor), factor);
+
+  g_snprintf (buffer, sizeof (buffer), "%d", exif_unit);
+  gexiv2_metadata_set_tag_string (GEXIV2_METADATA (metadata),
+                                  "Exif.Image.ResolutionUnit", buffer);
+}
+
+/**
+ * gimp_metadata_get_colorspace:
+ * @metadata: A #GimpMetadata instance.
+ *
+ * Returns values based on Exif.Photo.ColorSpace, Xmp.exif.ColorSpace,
+ * Exif.Iop.InteroperabilityIndex, Exif.Nikon3.ColorSpace,
+ * Exif.Canon.ColorSpace of @metadata.
+ *
+ * Return value: The colorspace specified by above tags.
+ *
+ * Since: 2.10
+ */
+GimpMetadataColorspace
+gimp_metadata_get_colorspace (GimpMetadata *metadata)
+{
+  glong exif_cs = -1;
+
+  g_return_val_if_fail (GIMP_IS_METADATA (metadata),
+                        GIMP_METADATA_COLORSPACE_UNSPECIFIED);
+
+  /*  the logic here was mostly taken from darktable and libkexiv2  */
+
+  if (gexiv2_metadata_has_tag (GEXIV2_METADATA (metadata),
+                               "Exif.Photo.ColorSpace"))
+    {
+      exif_cs = gexiv2_metadata_get_tag_long (GEXIV2_METADATA (metadata),
+                                              "Exif.Photo.ColorSpace");
+    }
+  else if (gexiv2_metadata_has_tag (GEXIV2_METADATA (metadata),
+                                    "Xmp.exif.ColorSpace"))
+    {
+      exif_cs = gexiv2_metadata_get_tag_long (GEXIV2_METADATA (metadata),
+                                              "Xmp.exif.ColorSpace");
+    }
+
+  if (exif_cs == 0x01)
+    {
+      return GIMP_METADATA_COLORSPACE_SRGB;
+    }
+  else if (exif_cs == 0x02)
+    {
+      return GIMP_METADATA_COLORSPACE_ADOBERGB;
+    }
+  else
+    {
+      if (exif_cs == 0xffff)
+        {
+          gchar *iop_index;
+
+          iop_index = gexiv2_metadata_get_tag_string (GEXIV2_METADATA (metadata),
+                                                      "Exif.Iop.InteroperabilityIndex");
+
+          if (! g_strcmp0 (iop_index, "R03"))
+            {
+              g_free (iop_index);
+
+              return GIMP_METADATA_COLORSPACE_ADOBERGB;
+            }
+          else if (! g_strcmp0 (iop_index, "R98"))
+            {
+              g_free (iop_index);
+
+              return GIMP_METADATA_COLORSPACE_SRGB;
+            }
+
+          g_free (iop_index);
+        }
+
+      if (gexiv2_metadata_has_tag (GEXIV2_METADATA (metadata),
+                                   "Exif.Nikon3.ColorSpace"))
+        {
+          glong nikon_cs;
+
+          nikon_cs = gexiv2_metadata_get_tag_long (GEXIV2_METADATA (metadata),
+                                                   "Exif.Nikon3.ColorSpace");
+
+          if (nikon_cs == 0x01)
+            {
+              return GIMP_METADATA_COLORSPACE_SRGB;
+            }
+          else if (nikon_cs == 0x02)
+            {
+              return GIMP_METADATA_COLORSPACE_ADOBERGB;
+            }
+        }
+
+      if (gexiv2_metadata_has_tag (GEXIV2_METADATA (metadata),
+                                   "Exif.Canon.ColorSpace"))
+        {
+          glong canon_cs;
+
+          canon_cs = gexiv2_metadata_get_tag_long (GEXIV2_METADATA (metadata),
+                                                   "Exif.Canon.ColorSpace");
+
+          if (canon_cs == 0x01)
+            {
+              return GIMP_METADATA_COLORSPACE_SRGB;
+            }
+          else if (canon_cs == 0x02)
+            {
+              return GIMP_METADATA_COLORSPACE_ADOBERGB;
+            }
+        }
+
+      if (exif_cs == 0xffff)
+        return GIMP_METADATA_COLORSPACE_UNCALIBRATED;
+    }
+
+  return GIMP_METADATA_COLORSPACE_UNSPECIFIED;
+}
+
+/**
+ * gimp_metadata_set_colorspace:
+ * @metadata:   A #GimpMetadata instance.
+ * @colorspace: The color space.
+ *
+ * Sets Exif.Photo.ColorSpace, Xmp.exif.ColorSpace,
+ * Exif.Iop.InteroperabilityIndex, Exif.Nikon3.ColorSpace,
+ * Exif.Canon.ColorSpace of @metadata.
+ *
+ * Since: 2.10
+ */
+void
+gimp_metadata_set_colorspace (GimpMetadata           *metadata,
+                              GimpMetadataColorspace  colorspace)
+{
+  GExiv2Metadata *g2metadata = GEXIV2_METADATA (metadata);
+
+  switch (colorspace)
+    {
+    case GIMP_METADATA_COLORSPACE_UNSPECIFIED:
+      gexiv2_metadata_clear_tag (g2metadata, "Exif.Photo.ColorSpace");
+      gexiv2_metadata_clear_tag (g2metadata, "Xmp.exif.ColorSpace");
+      gexiv2_metadata_clear_tag (g2metadata, "Exif.Iop.InteroperabilityIndex");
+      gexiv2_metadata_clear_tag (g2metadata, "Exif.Nikon3.ColorSpace");
+      gexiv2_metadata_clear_tag (g2metadata, "Exif.Canon.ColorSpace");
+      break;
+
+    case GIMP_METADATA_COLORSPACE_UNCALIBRATED:
+      gexiv2_metadata_set_tag_long (g2metadata, "Exif.Photo.ColorSpace", 0xffff);
+      if (gexiv2_metadata_has_tag (g2metadata, "Xmp.exif.ColorSpace"))
+        gexiv2_metadata_set_tag_long (g2metadata, "Xmp.exif.ColorSpace", 0xffff);
+      gexiv2_metadata_clear_tag (g2metadata, "Exif.Iop.InteroperabilityIndex");
+      gexiv2_metadata_clear_tag (g2metadata, "Exif.Nikon3.ColorSpace");
+      gexiv2_metadata_clear_tag (g2metadata, "Exif.Canon.ColorSpace");
+      break;
+
+    case GIMP_METADATA_COLORSPACE_SRGB:
+      gexiv2_metadata_set_tag_long (g2metadata, "Exif.Photo.ColorSpace", 0x01);
+
+      if (gexiv2_metadata_has_tag (g2metadata, "Xmp.exif.ColorSpace"))
+        gexiv2_metadata_set_tag_long (g2metadata, "Xmp.exif.ColorSpace", 0x01);
+
+      if (gexiv2_metadata_has_tag (g2metadata, "Exif.Iop.InteroperabilityIndex"))
+        gexiv2_metadata_set_tag_string (g2metadata,
+                                        "Exif.Iop.InteroperabilityIndex", "R98");
+
+      if (gexiv2_metadata_has_tag (g2metadata, "Exif.Nikon3.ColorSpace"))
+        gexiv2_metadata_set_tag_long (g2metadata, "Exif.Nikon3.ColorSpace", 0x01);
+
+      if (gexiv2_metadata_has_tag (g2metadata, "Exif.Canon.ColorSpace"))
+        gexiv2_metadata_set_tag_long (g2metadata, "Exif.Canon.ColorSpace", 0x01);
+      break;
+
+    case GIMP_METADATA_COLORSPACE_ADOBERGB:
+      gexiv2_metadata_set_tag_long (g2metadata, "Exif.Photo.ColorSpace", 0x02);
+
+      if (gexiv2_metadata_has_tag (g2metadata, "Xmp.exif.ColorSpace"))
+        gexiv2_metadata_set_tag_long (g2metadata, "Xmp.exif.ColorSpace", 0x02);
+
+      if (gexiv2_metadata_has_tag (g2metadata, "Exif.Iop.InteroperabilityIndex"))
+        gexiv2_metadata_set_tag_string (g2metadata,
+                                        "Exif.Iop.InteroperabilityIndex", "R03");
+
+      if (gexiv2_metadata_has_tag (g2metadata, "Exif.Nikon3.ColorSpace"))
+        gexiv2_metadata_set_tag_long (g2metadata, "Exif.Nikon3.ColorSpace", 0x02);
+
+      if (gexiv2_metadata_has_tag (g2metadata, "Exif.Canon.ColorSpace"))
+        gexiv2_metadata_set_tag_long (g2metadata, "Exif.Canon.ColorSpace", 0x02);
+      break;
+    }
+}
+
+/**
+ * gimp_metadata_is_tag_supported:
+ * @tag:       A metadata tag name
+ * @mime_type: A mime type
+ *
+ * Returns whether @tag is supported in a file of type @mime_type.
+ *
+ * Return value: %TRUE if the @tag supported with @mime_type, %FALSE otherwise.
+ *
+ * Since: 2.10
+ */
+gboolean
+gimp_metadata_is_tag_supported (const gchar *tag,
+                                const gchar *mime_type)
+{
+  gint j;
+
+  g_return_val_if_fail (tag != NULL, FALSE);
+  g_return_val_if_fail (mime_type != NULL, FALSE);
+
+  for (j = 0; j < G_N_ELEMENTS (unsupported_tags); j++)
+    {
+      if (g_str_has_prefix (tag, unsupported_tags[j]))
+        {
+          return FALSE;
+        }
+    }
+
+  if (! strcmp (mime_type, "image/jpeg"))
+    {
+      for (j = 0; j < G_N_ELEMENTS (tiff_tags); j++)
+        {
+          if (g_str_has_prefix (tag, tiff_tags[j]))
+            {
+              return FALSE;
+            }
+        }
+    }
+  else if (! strcmp (mime_type, "image/tiff"))
+    {
+      for (j = 0; j < G_N_ELEMENTS (jpeg_tags); j++)
+        {
+          if (g_str_has_prefix (tag, jpeg_tags[j]))
+            {
+              return FALSE;
+            }
+        }
+    }
+
+  return TRUE;
+}
+
+
+/* private functions */
+
+static GQuark
+gimp_metadata_error_quark (void)
+{
+  static GQuark quark = 0;
+
+  if (G_UNLIKELY (quark == 0))
+    quark = g_quark_from_static_string ("gimp-metadata-error-quark");
+
+  return quark;
+}
+
+static void
+gimp_metadata_copy_tag (GExiv2Metadata *src,
+                        GExiv2Metadata *dest,
+                        const gchar    *tag)
+{
+#if GEXIV2_CHECK_VERSION(0, 12, 2)
+  gchar  **values;
+  GError  *error = NULL;
+
+  values = gexiv2_metadata_try_get_tag_multiple (src, tag, &error);
+
+  if (error)
+    {
+      g_printerr ("%s: %s\n", G_STRFUNC, error->message);
+      g_clear_error (&error);
+      g_strfreev (values);
+    }
+  else if (values)
+    {
+      gexiv2_metadata_try_set_tag_multiple (dest, tag, (const gchar **) values, &error);
+      if (error)
+        {
+          g_warning ("%s: failed to set multiple metadata '%s': %s\n",
+                     G_STRFUNC, tag, error->message);
+          g_clear_error (&error);
+        }
+
+      g_strfreev (values);
+    }
+  else
+    {
+      gchar *value = gexiv2_metadata_try_get_tag_string (src, tag, &error);
+
+      if (value)
+        {
+          gexiv2_metadata_try_set_tag_string (dest, tag, value, &error);
+          if (error)
+            {
+              g_warning ("%s: failed to set metadata '%s': %s\n",
+                         G_STRFUNC, tag, error->message);
+              g_clear_error (&error);
+            }
+          g_free (value);
+        }
+      else if (error)
+        {
+          g_warning ("%s: failed to get metadata '%s': %s\n",
+                     G_STRFUNC, tag, error->message);
+          g_clear_error (&error);
+        }
+    }
+#else
+  gchar **values = gexiv2_metadata_get_tag_multiple (src, tag);
+
+  if (values)
+    {
+      gexiv2_metadata_set_tag_multiple (dest, tag, (const gchar **) values);
+      g_strfreev (values);
+    }
+  else
+    {
+      gchar *value = gexiv2_metadata_get_tag_string (src, tag);
+
+      if (value)
+        {
+          gexiv2_metadata_set_tag_string (dest, tag, value);
+          g_free (value);
+        }
+    }
+#endif
+}
+
+static void
+gimp_metadata_copy_tags (GExiv2Metadata  *src,
+                         GExiv2Metadata  *dest,
+                         const gchar    **tags)
+{
+  gint i;
+
+  for (i = 0; tags[i] != NULL; i++)
+    {
+      /* don't copy the same tag multiple times */
+      if (i > 0 && ! strcmp (tags[i], tags[i - 1]))
+        continue;
+
+      gimp_metadata_copy_tag (src, dest, tags[i]);
+    }
+ }
+
+static void
+gimp_metadata_add (GimpMetadata *src,
+                   GimpMetadata *dest)
+{
+  GExiv2Metadata *g2src  = GEXIV2_METADATA (src);
+  GExiv2Metadata *g2dest = GEXIV2_METADATA (dest);
+
+  if (gexiv2_metadata_get_supports_exif (g2src) &&
+      gexiv2_metadata_get_supports_exif (g2dest))
+    {
+      gchar **exif_tags = gexiv2_metadata_get_exif_tags (g2src);
+
+      if (exif_tags)
+        {
+          gimp_metadata_copy_tags (g2src, g2dest,
+                                   (const gchar **) exif_tags);
+          g_strfreev (exif_tags);
+        }
+    }
+
+  if (gexiv2_metadata_get_supports_xmp (g2src) &&
+      gexiv2_metadata_get_supports_xmp (g2dest))
+    {
+      gchar **xmp_tags = gexiv2_metadata_get_xmp_tags (g2src);
+
+      if (xmp_tags)
+        {
+          gimp_metadata_copy_tags (g2src, g2dest,
+                                   (const gchar **) xmp_tags);
+          g_strfreev (xmp_tags);
+        }
+    }
+
+  if (gexiv2_metadata_get_supports_iptc (g2src) &&
+      gexiv2_metadata_get_supports_iptc (g2dest))
+    {
+      gchar **iptc_tags = gexiv2_metadata_get_iptc_tags (g2src);
+
+      if (iptc_tags)
+        {
+          gimp_metadata_copy_tags (g2src, g2dest,
+                                   (const gchar **) iptc_tags);
+          g_strfreev (iptc_tags);
+        }
+    }
+}