from kivy.app import App
from kivy.uix.button import Button
from kivy.uix.boxlayout import BoxLayout
from kivy.core.image import Image
from kivy.uix.gridlayout import GridLayout
from kivy.graphics.fbo import Fbo
from kivy.graphics.texture import Texture
from functools import partial
from kivy.uix.widget import Widget
from kivy.graphics.opengl import glReadPixels,GL_RGBA, GL_UNSIGNED_BYTE
from kivy.graphics import *

class Guardar(Widget):

    def guardar_canvas2(self,widget):
        if widget.parent is not None:
            canvas_parent_index = widget.parent.canvas.indexof(widget.canvas)
            if canvas_parent_index > -1:
                widget.parent.canvas.remove(widget.canvas)

        fbo = Fbo(size=widget.size, with_stencilbuffer=True)

        with fbo:
            ClearColor(0, 0, 0, 1)
            ClearBuffers()
            Scale(1, -1, 1)
            Translate(-widget.x, -widget.y - widget.height, 0)

        fbo.add(widget.canvas)
        fbo.draw()
        fbo.texture.save("gidhup.png", flipped=False)
        fbo.remove(widget.canvas)

        if widget.parent is not None and canvas_parent_index > -1:
            widget.parent.canvas.insert(canvas_parent_index, widget.canvas)

        return True

class TestApp(App):

    def guardar(self,ins,*args):
        Guardar().guardar_canvas2(ins)

    def build(self):
        self.bx=BoxLayout(orientation="vertical")
        self.bx2=BoxLayout()
        self.gl=GridLayout(cols=5,rows=5)
        for i in range(25):
            self.gl.add_widget(Button(text=str(i)))
        btn=Button(on_release=partial(self.guardar, self.bx2),text='Save canvas :)')
        self.bx2.add_widget(self.gl)
        self.bx.add_widget(self.bx2)
        self.bx.add_widget(btn)
        return self.bx

TestApp().run()