tag: Adds GST_TAG_CAPTURING_METERING_MODE

Adds a tag to inform what mode was used by a camera to calculate
the picture capturing exposure

Also adds mapping to exif and tests

API: GST_TAG_CAPTURING_METERING_MODE

https://bugzilla.gnome.org/show_bug.cgi?id=631773

docs/libs/gst-plugins-base-libs-sections.txt

@@ -1669,6 +1669,7 @@ GST_TAG_CAPTURING_SATURATION
 GST_TAG_CAPTURING_SHARPNESS
 GST_TAG_CAPTURING_FLASH_FIRED
 GST_TAG_CAPTURING_FLASH_MODE
+GST_TAG_CAPTURING_METERING_MODE
 GST_TAG_IMAGE_HORIZONTAL_PPI
 GST_TAG_IMAGE_VERTICAL_PPI
 gst_tag_register_musicbrainz_tags

gst-libs/gst/tag/gstexiftag.c

@@ -234,6 +234,7 @@ EXIF_SERIALIZATION_DESERIALIZATION_FUNC (gain_control);
 EXIF_SERIALIZATION_DESERIALIZATION_FUNC (geo_coordinate);
 EXIF_SERIALIZATION_DESERIALIZATION_FUNC (geo_direction);
 EXIF_SERIALIZATION_DESERIALIZATION_FUNC (geo_elevation);
+EXIF_SERIALIZATION_DESERIALIZATION_FUNC (metering_mode);
 EXIF_SERIALIZATION_DESERIALIZATION_FUNC (orientation);
 EXIF_SERIALIZATION_DESERIALIZATION_FUNC (saturation);
 EXIF_SERIALIZATION_DESERIALIZATION_FUNC (scene_capture_type);
@@ -284,6 +285,7 @@ EXIF_DESERIALIZATION_FUNC (add_to_pending_tags);
 #define EXIF_TAG_DATE_TIME_DIGITIZED 0x9004
 #define EXIF_TAG_SHUTTER_SPEED_VALUE 0x9201
 #define EXIF_TAG_APERTURE_VALUE 0x9202
+#define EXIF_TAG_METERING_MODE 0x9207
 #define EXIF_TAG_FLASH 0x9209
 #define EXIF_TAG_FOCAL_LENGTH 0x920A
 #define EXIF_TAG_MAKER_NOTE 0x927C
@@ -368,6 +370,8 @@ static const GstExifTagMatch tag_map_exif[] = {
   {GST_TAG_CAPTURING_FOCAL_RATIO, EXIF_TAG_APERTURE_VALUE, EXIF_TYPE_RATIONAL,
         0,
       serialize_aperture_value, deserialize_aperture_value},
+  {GST_TAG_CAPTURING_METERING_MODE, EXIF_TAG_METERING_MODE, EXIF_TYPE_SHORT, 0,
+      serialize_metering_mode, deserialize_metering_mode},
   {GST_TAG_CAPTURING_FLASH_FIRED, EXIF_TAG_FLASH, EXIF_TYPE_SHORT, 0,
       serialize_flash, deserialize_flash},
   {GST_TAG_CAPTURING_FOCAL_LENGTH, EXIF_TAG_FOCAL_LENGTH, EXIF_TYPE_RATIONAL, 0,
@@ -1759,6 +1763,8 @@ EXIF_SERIALIZATION_DESERIALIZATION_MAP_STRING_TO_INT_FUNC (exposure_program,
     capturing_exposure_program);
 EXIF_SERIALIZATION_DESERIALIZATION_MAP_STRING_TO_INT_FUNC (gain_control,
     capturing_gain_adjustment);
+EXIF_SERIALIZATION_DESERIALIZATION_MAP_STRING_TO_INT_FUNC (metering_mode,
+    capturing_metering_mode);
 EXIF_SERIALIZATION_DESERIALIZATION_MAP_STRING_TO_INT_FUNC (orientation,
     image_orientation);
 EXIF_SERIALIZATION_DESERIALIZATION_MAP_STRING_TO_INT_FUNC (saturation,

gst-libs/gst/tag/gsttageditingprivate.c

@@ -374,3 +374,57 @@ __exif_tag_capturing_sharpness_from_exif_value (gint value)
   return __exif_tag_capturing_contrast_sharpness_from_exif_value (value,
       "sharpness");
 }
+
+gint
+__exif_tag_capturing_metering_mode_to_exif_value (const gchar * str)
+{
+  if (str == NULL)
+    goto end;
+
+  if (strcmp (str, "unknown") == 0)
+    return 0;
+  else if (strcmp (str, "average") == 0)
+    return 1;
+  else if (strcmp (str, "center-weighted-average") == 0)
+    return 2;
+  else if (strcmp (str, "spot") == 0)
+    return 3;
+  else if (strcmp (str, "multi-spot") == 0)
+    return 4;
+  else if (strcmp (str, "pattern") == 0)
+    return 5;
+  else if (strcmp (str, "partial") == 0)
+    return 6;
+  else if (strcmp (str, "other") == 0)
+    return 255;
+
+end:
+  GST_WARNING ("Invalid metering mode type: %s", str);
+  return -1;
+}
+
+const gchar *
+__exif_tag_capturing_metering_mode_from_exif_value (gint value)
+{
+  switch (value) {
+    case 0:
+      return "unknown";
+    case 1:
+      return "average";
+    case 2:
+      return "center-weighted-average";
+    case 3:
+      return "spot";
+    case 4:
+      return "multi-spot";
+    case 5:
+      return "pattern";
+    case 6:
+      return "partial";
+    case 255:
+      return "other";
+    default:
+      GST_WARNING ("Invalid metering mode type: %d", value);
+      return NULL;
+  }
+}

gst-libs/gst/tag/gsttageditingprivate.h

@@ -62,6 +62,9 @@ const gchar * __exif_tag_capturing_saturation_from_exif_value (gint value);
 gint __exif_tag_capturing_sharpness_to_exif_value (const gchar * str);
 const gchar * __exif_tag_capturing_sharpness_from_exif_value (gint value);
 
+gint __exif_tag_capturing_metering_mode_to_exif_value (const gchar * str);
+const gchar * __exif_tag_capturing_metering_mode_from_exif_value (gint value);
+
 G_END_DECLS
 
 #endif /* __GST_TAG_EDIT_PRIVATE_H__ */

gst-libs/gst/tag/tag.h

@@ -320,6 +320,25 @@ G_BEGIN_DECLS
  */
 #define GST_TAG_CAPTURING_FLASH_MODE         "capturing-flash-mode"
 
+/**
+ * GST_TAG_CAPTURING_METERING_MODE:
+ *
+ * Defines the way a camera determines the exposure. (string)
+ *
+ * The allowed values are:
+ *   "unknown"
+ *   "average"
+ *   "center-weighted-average"
+ *   "spot"
+ *   "multi-spot"
+ *   "pattern"
+ *   "partial"
+ *   "other"
+ *
+ * Since: 0.10.31
+ */
+#define GST_TAG_CAPTURING_METERING_MODE      "capturing-metering-mode"
+
 /**
  * GST_TAG_IMAGE_HORIZONTAL_PPI:
  *

gst-libs/gst/tag/tags.c

@@ -162,11 +162,16 @@ gst_tag_register_tags_internal (gpointer unused)
 
   gst_tag_register (GST_TAG_CAPTURING_FLASH_FIRED, GST_TAG_FLAG_META,
       G_TYPE_BOOLEAN, _("capturing flash fired"),
-      _("If the flash fired while capturing and image"), NULL);
+      _("If the flash fired while capturing an image"), NULL);
 
   gst_tag_register (GST_TAG_CAPTURING_FLASH_MODE, GST_TAG_FLAG_META,
       G_TYPE_STRING, _("capturing flash mode"),
-      _("The selected flash mode while capturing and image"), NULL);
+      _("The selected flash mode while capturing an image"), NULL);
+
+  gst_tag_register (GST_TAG_CAPTURING_METERING_MODE, GST_TAG_FLAG_META,
+      G_TYPE_STRING, _("capturing metering mode"),
+      _("The metering mode used while determining exposure for capturing an"
+          " image"), NULL);
 
   gst_tag_register (GST_TAG_IMAGE_HORIZONTAL_PPI, GST_TAG_FLAG_META,
       G_TYPE_DOUBLE, _("image horizontal ppi"),

tests/check/libs/tag.c

@@ -1394,6 +1394,31 @@ GST_START_TEST (test_exif_tags_serialization_deserialization)
   g_value_set_static_string (&value, "soft");
   do_simple_exif_tag_serialization_deserialization (GST_TAG_CAPTURING_SHARPNESS,
       &value);
+
+  g_value_set_static_string (&value, "unknown");
+  do_simple_exif_tag_serialization_deserialization
+      (GST_TAG_CAPTURING_METERING_MODE, &value);
+  g_value_set_static_string (&value, "average");
+  do_simple_exif_tag_serialization_deserialization
+      (GST_TAG_CAPTURING_METERING_MODE, &value);
+  g_value_set_static_string (&value, "center-weighted-average");
+  do_simple_exif_tag_serialization_deserialization
+      (GST_TAG_CAPTURING_METERING_MODE, &value);
+  g_value_set_static_string (&value, "spot");
+  do_simple_exif_tag_serialization_deserialization
+      (GST_TAG_CAPTURING_METERING_MODE, &value);
+  g_value_set_static_string (&value, "multi-spot");
+  do_simple_exif_tag_serialization_deserialization
+      (GST_TAG_CAPTURING_METERING_MODE, &value);
+  g_value_set_static_string (&value, "pattern");
+  do_simple_exif_tag_serialization_deserialization
+      (GST_TAG_CAPTURING_METERING_MODE, &value);
+  g_value_set_static_string (&value, "partial");
+  do_simple_exif_tag_serialization_deserialization
+      (GST_TAG_CAPTURING_METERING_MODE, &value);
+  g_value_set_static_string (&value, "other");
+  do_simple_exif_tag_serialization_deserialization
+      (GST_TAG_CAPTURING_METERING_MODE, &value);
   g_value_unset (&value);
 
   g_value_init (&value, G_TYPE_DOUBLE);