tag: exif: Adds mapping for GST_TAG_CAPTURING_EXPOSURE_COMPENSATION

Adds mapping for GST_TAG_CAPTURING_EXPOSURE_COMPENSATION for exif
library.

Includes unit tests.

gst-libs/gst/tag/gstexiftag.c

@@ -301,6 +301,7 @@ 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_EXPOSURE_BIAS 0x9204
 #define EXIF_TAG_METERING_MODE 0x9207
 #define EXIF_TAG_FLASH 0x9209
 #define EXIF_TAG_FOCAL_LENGTH 0x920A
@@ -388,6 +389,8 @@ 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_EXPOSURE_COMPENSATION, EXIF_TAG_EXPOSURE_BIAS,
+      EXIF_TYPE_SRATIONAL, 0, NULL, NULL},
   {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,
@@ -920,6 +923,41 @@ write_exif_rational_tag_from_taglist (GstExifWriter * writer,
   }
 }
 
+static void
+write_exif_signed_rational_tag_from_taglist (GstExifWriter * writer,
+    const GstTagList * taglist, const GstExifTagMatch * exiftag)
+{
+  const GValue *value;
+  gdouble num = 0;
+  gint tag_size = gst_tag_list_get_tag_size (taglist, exiftag->gst_tag);
+
+  if (tag_size != 1) {
+    GST_WARNING ("Only the first item in the taglist will be serialized");
+    return;
+  }
+
+  value = gst_tag_list_get_value_index (taglist, exiftag->gst_tag, 0);
+
+  /* do some conversion if needed */
+  switch (G_VALUE_TYPE (value)) {
+    case G_TYPE_DOUBLE:
+      num = g_value_get_double (value);
+      gst_exif_writer_write_signed_rational_tag_from_double (writer,
+          exiftag->exif_tag, num);
+      break;
+    default:
+      if (G_VALUE_TYPE (value) == GST_TYPE_FRACTION) {
+        gst_exif_writer_write_signed_rational_tag (writer, exiftag->exif_tag,
+            gst_value_get_fraction_numerator (value),
+            gst_value_get_fraction_denominator (value));
+      } else {
+        GST_WARNING ("Conversion from %s to signed rational not supported",
+            G_VALUE_TYPE_NAME (value));
+      }
+      break;
+  }
+}
+
 static void
 write_exif_integer_tag_from_taglist (GstExifWriter * writer,
     const GstTagList * taglist, const GstExifTagMatch * exiftag)
@@ -980,6 +1018,9 @@ write_exif_tag_from_taglist (GstExifWriter * writer, const GstTagList * taglist,
     case EXIF_TYPE_RATIONAL:
       write_exif_rational_tag_from_taglist (writer, taglist, exiftag);
       break;
+    case EXIF_TYPE_SRATIONAL:
+      write_exif_signed_rational_tag_from_taglist (writer, taglist, exiftag);
+      break;
     case EXIF_TYPE_LONG:
     case EXIF_TYPE_SHORT:
       write_exif_integer_tag_from_taglist (writer, taglist, exiftag);
@@ -1561,6 +1602,10 @@ parse_exif_ifd (GstExifReader * exif_reader, gint buf_offset,
         parse_exif_rational_tag (exif_reader, tag_map[map_index].gst_tag,
             tagdata.count, tagdata.offset, 1, FALSE);
         break;
+      case EXIF_TYPE_SRATIONAL:
+        parse_exif_rational_tag (exif_reader, tag_map[map_index].gst_tag,
+            tagdata.count, tagdata.offset, 1, TRUE);
+        break;
       case EXIF_TYPE_UNDEFINED:
         parse_exif_undefined_tag (exif_reader, &tag_map[map_index],
             tagdata.count, tagdata.offset, tagdata.offset_as_data);

tests/check/libs/tag.c

@@ -1525,6 +1525,16 @@ GST_START_TEST (test_exif_tags_serialization_deserialization)
   g_value_set_double (&value, 600.0);
   do_simple_exif_tag_serialization_deserialization
       (GST_TAG_IMAGE_VERTICAL_PPI, &value);
+
+  g_value_set_double (&value, 0.0);
+  do_simple_exif_tag_serialization_deserialization
+      (GST_TAG_CAPTURING_EXPOSURE_COMPENSATION, &value);
+  g_value_set_double (&value, 1.0);
+  do_simple_exif_tag_serialization_deserialization
+      (GST_TAG_CAPTURING_EXPOSURE_COMPENSATION, &value);
+  g_value_set_double (&value, -2.5);
+  do_simple_exif_tag_serialization_deserialization
+      (GST_TAG_CAPTURING_EXPOSURE_COMPENSATION, &value);
   g_value_unset (&value);
 
   g_value_init (&value, G_TYPE_INT);