I would love to use this action type, but the rescaled art has noticeable artifacting and there's no way to set the compression level or interpolation algorithm for a more satisfactory quality to size ratio. In the meantime, I'll just keep using GIMP.
Can you provide an example cover file that produces such bad results? I'm using highest quality on the compression level and was satisfied with the results in my extensive testing.
can verify. example: https://imgur.com/a/0nbtgnt
(edited with more descriptive example)