scatterlayout is a grid of overlapping buttons

I’m not sure but is this what you want?

from kivy.config import Config
Config.set('modules', 'showborder', '')

from kivy.app import App
from kivy.lang import Builder
from kivy.factory import Factory as F


class MyScatter(F.Scatter):
    pass


Builder.load_string('''
<MyScatter>:
    scale: 1
    do_scale: True 
    do_translation: True
    do_rotation: False
    size_hint: None, None
    size: img.size
    auto_bring_to_front: False
    Image:
        id: img
        source: 'data/logo/kivy-icon-256.png'
        # size_hint: (0.43, 0.6)
        # pos_hint: {'center_x': 0.33, 'center_y': 0.5}
        keep_ratio: True
        size: self.texture.size if self.texture else (0, 0)
''')


class MyApp(App):
    def build(self):

        mainbox = F.FloatLayout()
        self.ms = MyScatter()
        mainbox.add_widget(self.ms)
        mainbox.add_widget(F.Button(text="Fwd",
                                  font_size="17dp",
                                  size_hint=(.075, .15),
                                  pos_hint={"left":1,
                                            "center_y":0.5},
                                  on_press=print))

        return mainbox


MyApp().run()