Default [Q] Google Music and album art crop

I use Google Music app on Android 4.4.2 and used the Album Art Grabber app to get all album arts and it works fine. Problem is, most album are zoomed and cropped and only show the middle part of the picture, which is not that great. I would much prefer to have the full picture with black bars on top/bottom. The app does not seems to have this feature already.

I have a Nexus 5, rooted with Xposed Framework. Anyone know if there's something for this? I'm also a programmer (nothing android related), if I knew where to look maybe I could try it myself.