[easytag] Add a TODO for METADATA_BLOCK_PICTURE colour depth

[David King <davidk src gnome org>]

commit 8a234621179ba9d92113bff68d766e5e5532b3c0
Author: David King <amigadave amigadave com>
Date:   Sun Mar 5 18:31:37 2017 +0000

    Add a TODO for METADATA_BLOCK_PICTURE colour depth

 src/tags/ogg_tag.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)
---
diff --git a/src/tags/ogg_tag.c b/src/tags/ogg_tag.c
index f9ad0fd..3ad4c8d 100644
--- a/src/tags/ogg_tag.c
+++ b/src/tags/ogg_tag.c
@@ -1113,8 +1113,9 @@ ogg_tag_write_file_tag (const ET_File *ETFile,
         convert_to_byte_array (pic->height, array);
         add_to_guchar_str (ustring, &ustring_len, array, 4);
 
-        /* GdkPicbuf only supports images with 8 bits per sample. */
-        convert_to_byte_array (8, array);
+        /* TODO: Determine the depth per pixel by querying the pixbuf to see
+         * whether an alpha channel is present. */
+        convert_to_byte_array (0, array);
         add_to_guchar_str (ustring, &ustring_len, array, 4);
 
         /* Non-indexed images should set this to zero. */