sane-tag-music: support "artist.png" artist images

pkgs/additional/sane-scripts/src/sane-tag-music

@@ -94,6 +94,12 @@ logger = logging.getLogger(__name__)
 
 kks = pykakasi.kakasi()
 
+IMAGE_EXTENSIONS = [
+  "jpg",
+  "jpeg",
+  "png",
+]
+
 class MediaType(Enum):
     Audio = "audio"
     Image = "image"
@@ -333,9 +339,24 @@ class Tags:
         if loose_compare_str(self.album[0], "Singles"):
             self.tracknumber = []
 
+    def is_artist_item(self, ext: str) -> bool:
+        """
+        some items are associated with the artist instead of with an album.
+        for example, `artist.png`.
+        it's tough to distinguish such an item from an incomplete tag,
+        so we special-case them.
+        """
+        title = self.title[0].lower() if len(self.title) == 1 else ""
+        return ext.lower() in IMAGE_EXTENSIONS \
+            and not self.producer \
+            and (self.albumartist or self.artist) \
+            and not self.album \
+            and title == "artist"
+
     def to_path(self, ext: str) -> str | None:
+        is_artist_item = self.is_artist_item(ext)
         artist = self.albumartist or self.artist
-        if not (artist and self.album and self.title and ext):
+        if not (artist and self.album and self.title and ext or is_artist_item):
             return None
 
         artist = clean_fields_for_fs(artist, single_fields=False)
@@ -345,6 +366,9 @@ class Tags:
         title = clean_fields_for_fs(self.title)
         filename = clean_fields_for_fs(trackno + [ f"{title}.{ext}" ])
 
+        if is_artist_item:
+            return os.path.join(artist, filename)
+
         if not (artist and album and title):
             return None
 
@@ -459,13 +483,17 @@ class MediaFile:
     def __repr__(self) -> str:
         return self.path_
 
+    @property
+    def ext(self):
+        return os.path.splitext(self.path_)[1][1:]
+
     @staticmethod
     def new(f: 'str | MediaFile | None') -> 'MediaFile | None':
         if f is None:
             return None
         if isinstance(f, str):
             lower = f.lower()
-            if lower.endswith(".png") or lower.endswith(".jpg") or lower.endswith("jpeg"):
+            if any(lower.endswith(f".{e}") for e in IMAGE_EXTENSIONS):
                 f = ImageFile(f)
             else:
                 f = AudioFile(f)
@@ -630,7 +658,12 @@ class Tagger:
     def is_sufficiently_tagged(self, file_: MediaFile) -> bool:
         tags = file_.tags_on_disk()
         # N.B.: track number isn't wholly necessary; just a nice-to-have.
-        return (tags.artist or tags.albumartist) and tags.album and tags.title
+        if (tags.artist or tags.albumartist) and tags.album and tags.title:
+            return True
+        if tags.is_artist_item(file_.ext):
+            # artist image, not part of any album
+            return True
+        return False
 
     def tag_file(self, file_: MediaFile) -> None:
         old_tags = file_.tags_on_disk()