Anyone know how to rip sprites off of the Beyblade Burst App?

Been nagging this thought for days, but does anyone know how I can easily rip off Avatar sprites from the Beyblade Burst App? I always have to revert to the old fashioned way where I take a screenshot for the Avatar Attack then remove the background via Paint.net software just to use the transperent Avatar. 

For example in this image.

Though I substantially utilize this method as an alternative way for 'getting' the sprites, I feel as if the cut outs are just misreable and does not fully suit my need for thumbnails.
I have seen Zankye successfully rip the avatars off of the app, for instance he ripped off a Garuda for one of his video thumbnails.



I personally never asked him about this since it seemed a little pointless to nag this potential concern, I tried to extract the App's APK files through Winrar. 
In results, I never found image files regarding the Burst Avatars. I only found the loading screen, app icon, and other assets unrelated to my problem.

Any help would be appreciated.