If I use 4 images in my App, all in the drawable folder, and they are the same image, does Android compile recognize it, and only saves the bitsequence ones?
Background: Using identical pictures in different parts, with the option to adjust later, but currently identical (e.g. btn_menu + btn_web)
No, it does not. All your PNGs are saved as-is in
.apk, which is, by the way, a kind of ZIP archive – so you can use any archiver to see its contents and all of your PNGs untouched.