How to set a screen background image in Kivy -

i know how make color background can't seem find useful setting image background , grateful code.

here .py file:

from kivy.app import app kivy.uix.screenmanager import screenmanager, screen, fadetransition kivy.uix.boxlayout import boxlayout kivy.uix.floatlayout import floatlayout kivy.uix.gridlayout import gridlayout #from kivy.uix.label import label kivy.uix.button import button kivy.core.window import window kivy.core.image import image #from kivy.graphics import borderimage kivy.graphics import color, rectangle #from kivy.uix.image import asyncimage   class startscreen(screen):     pass  class gamescreen(screen):     pass  class rootscreen(screenmanager):     pass   class mainapp(app):     def build(self):         return rootscreen()  if __name__ == "__main__":     mainapp().run() 

and .kv file:

#:import fadetransition kivy.uix.screenmanager.fadetransition  <rootscreen>:     transition: fadetransition()      startscreen:     gamescreen:  <startscreen>:     name: "start"     canvas.before:         rectangle:             pos: self.pos             size: self.size         image:             source: "lights.png"     floatlayout:         image:     # part doesn't seem work             source: "lights.png"             allow_stretch: true             keep_ratio: false             size_hint: 1, 1         button:             text: "play!"             size_hint: 0.4, 0.3             pos_hint: {'center_x':.5, 'center_y':.5}             font_size: 70             on_release: root.manager.current = "game" <gamescreen>:     name: "game"     floatlayout:         button:             text: "nazaj!"             font_size: 70             on_release: root.manager.current  = "start" 

canvas.before:         rectangle:             pos: self.pos             size: self.size         image:             source: "lights.png" 

image widget, can't place on canvas.

what *can either set source rectangle:

canvas.before:         rectangle:             pos: self.pos             size: self.size             source: 'lights.png' 

...or place image behind other widgets putting them in container layout.