BorderImage example, pure python and kv.

main.py

from kivy.app import App
from kivy.uix.widget import Widget
from kivy.uix.button import Button
from kivy.graphics import BorderImage


class MyApp(App):
    def build(self):
        root = Widget()
        b = Button(center=(200, 200))
        root.add_widget(b)
        with b.canvas.before:
            BorderImage(
                size=(b.width + 100, b.height + 100),
                pos=(b.x - 50, b.y - 50),
                border=(10, 10, 10, 10),
                source='tex.png')

        return root


MyApp().run()

main_kv.py

from kivy.app import App
from kivy.lang import Builder

kv = '''
Widget:
    Button:
        pos: 200, 200
        canvas.before:
            BorderImage:
                source: 'tex.png'
                pos: self.x - 50, self.y - 50
                size: self.width + 100, self.height + 100
'''


class MyApp(App):
    def build(self):
        return Builder.load_string(kv)


MyApp().run()

tex.png

💖 💖 Thanks!