tagging.py: coverart rework documentation

docs/extensions/tagging.md

@@ -2,7 +2,7 @@
 title: Tag downloaded files using Mutagen
 ---
 
-Add episode and podcast titles to MP3/OGG tags.
+Add tags to MP3/MP4/OGG files after download.
 
 By default, this extension will:
    - Remove existing tags
@@ -16,26 +16,36 @@ Also available are writing the Subtitle tag and the Comments tag (both with the
 subtitle field), but the subtitle is often so long that it may cause problems with
 certain audio players, such as Rockbox players. These are disabled by default.
 
-This extension can optionally embed coverart - note that the coverart will not be
-standardized in any way, so Rockbox users be wary. This is disabled by default.
+This extension can optionally embed coverart - art can either be the channel artwork
+or episode-specific artwork already embedded in the file. By default, the episode
+artwork will be preferred if it is present - if not, the channel artwork will be used.
+
+Note that episode-specific artwork in MP4 files is currently not implemented.
+
+The artwork can optionally be normalized to the desired parameters - size and file type.
+By default, it will write 500px baseline JPEGs.
 
 This extension can optionally remove all tags instead of doing any of the above.
 This is disabled by default.
 
 ## Dependencies
 
-This extension requires python module `mutagen`.
+This extension requires python modules `mutagen` and `pillow`.
 
 | setting                                      | value      | description                                                                               | version           |
 |----------------------------------------------|------------|-------------------------------------------------------------------------------------------|-------------------|
 | extensions.tagging.strip\_album\_from\_title | **true**/false | Remove the Album tag from the Title tag if the Title begins with the same string as the Album tag | all |
 | extensions.tagging.genre\_tag                | Podcast    | Value for the Genre tag | all |
 | extensions.tagging.always\_remove\_tags      | true/**false** | Remove all tags instead of creating/adding tag information              | 3.5.0 and newer             |
-| extensions.tagging.auto\_embed\_coverart     | true/**false** | Embed channel cover art in file | git master branch |
 | extensions.tagging.set\_artist\_to\_album    | **True**/False | Set the Artist tag to the same as the existing Album tag | git master branch |
 | extensions.tagging.set\_version              | 4              | Sets the id3 version which will be written | git master branch |
 | extensions.tagging.modify\_tags              | **True**/False | Allow tags to be modified rather than simply added. If set to False, remove\_before\_modify has no effect | git master branch |
 | extensions.tagging.remove\_before\_modify    | **True**/False | Delete all existing tags prior to writing new tags | git master branch |
+| extensions.tagging.auto\_embed\_coverart           | true/**false** | Embed cover art in file | git master branch |
+| extensions.tagging.prefer\_channel\_coverart | true/**false** | Prefer embedding the channel coverart if available over the episode coverart | git master branch |
+| extensions.tagging.normalize\_coverart       | **true**/false | Normalize the coverart to the desired size and file type before embedding it | git master branch |
+| extensions.tagging.episode\_coverart\_size   | 500            | Desired size (in pixels) of coverart. Only used if normalize\_coverart is True | git master branch |
+| extensions.tagging.episode\_coverart\_filetype | 0 (JPEG)     | Desired filetype of coverart. integer value, maps to 0=JPEG, 1=PNG. Only used if normalize\_coverart is True | git master branch |
 | extensions.tagging.write\_title              | **True**/False | Write the title field | git master branch |
 | extensions.tagging.write\_album              | **True**/False | Write the album field | git master branch |
 | extensions.tagging.write\_subtitle           | True/**False** | Write the subtitle field | git master branch |