[gimp/gimp-2-10] libgimp: set subfiletype to FILETYPE_REDUCEDIMAGE when saving EXIF thumbnails.

[Jacob Boerema <jboerema src gnome org>]

commit 183900ca97bb7db2838487e1325d59bfb75b63fe
Author: Jacob Boerema <jgboerema gmail com>
Date:   Sat Aug 28 13:24:14 2021 -0400

    libgimp: set subfiletype to FILETYPE_REDUCEDIMAGE when saving EXIF thumbnails.

 libgimp/gimpimagemetadata.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
---
diff --git a/libgimp/gimpimagemetadata.c b/libgimp/gimpimagemetadata.c
index 52fad728c0..a8af509f8f 100644
--- a/libgimp/gimpimagemetadata.c
+++ b/libgimp/gimpimagemetadata.c
@@ -808,7 +808,10 @@ gimp_image_metadata_save_finish (gint32                  image_ID,
                                           "3");
           gexiv2_metadata_set_tag_string (new_g2metadata,
                                           "Exif.Thumbnail.PhotometricInterpretation",
-                                          "6");
+                                          "6"); /* old jpeg */
+          gexiv2_metadata_set_tag_string (new_g2metadata,
+                                          "Exif.Thumbnail.NewSubfileType",
+                                          "1"); /* reduced resolution image */
 
           g_free (thumb_buffer);
         }