Kivy - Get Image ROI Coordinates

Question

Я работаю над приложением, в котором я хочу загрузить изображение и выбрать область интереса региона. При выборе отображаются начальная и конечная координаты. С помощью виджета я могу получить координаты выделения (мышь вниз и мышь вверх) приложения Kivy. Но мне нужны именно точные координаты изображения. Есть ли способ получить ROI изображения?

import kivy
kivy.require("1.11.1")

from kivy.app import App
from kivy.uix.widget import Widget
from kivy.graphics.texture import Texture
from kivy.uix.image import Image
from kivy.uix.button import Button
from kivy.uix.label import Label

from kivy.uix.boxlayout import BoxLayout
from kivy.graphics import *

class TouchInput(Widget):
    def __init__(self, **kwargs):
        super(TouchInput, self).__init__(**kwargs)
        self.start_pos = [0, 0]
        self.end_pos = [0, 0]
        self.img_path = 'img.jpg'

    def but_press(self):
        print("But is pressed!")

    def on_touch_down(self, touch):
        with self.canvas:
            self.canvas.clear()
            # Load Image
            self.img = Image(source=self.img_path)
            self.img.allow_stretch = True
            self.img.keep_ratio = True
            self.img.size = self.size

            # Position set
            self.img.pos = (0, 0)
            self.img.opacity = 1


            self.start_pos = [touch.x, touch.y]
            print("Start pos:", self.start_pos)

    def on_touch_move(self, touch):
        rect_size = [10, 10]
        with self.canvas:
            self.canvas.clear()
            # Load Image
            self.img = Image(source=self.img_path)
            self.img.allow_stretch = True
            self.img.keep_ratio = True
            self.img.size = self.size
            # Position set
            self.img.pos = (0, 0)
            self.img.opacity = 1
            self.end_pos = [touch.x, touch.y]
            # print("End pos  :", self.end_pos)

            if self.start_pos == self.end_pos:
                print("Same position")

            elif (self.start_pos[0] < self.end_pos[0]) and (self.start_pos[1] < self.end_pos[1]):
                print("Top Right")
                rect_start_point = self.start_pos
                rect_size = [abs(self.start_pos[0] - self.end_pos[0]), abs(self.start_pos[1] - self.end_pos[1])]

                print("Pos:", self.start_pos, "Size:", rect_size)
                Color(rgba=(100 / 255, 143 / 255, 165 / 255, 0.6))
                self.rect = Rectangle(pos=rect_start_point, size=(rect_size))

            elif (self.start_pos[0] < self.end_pos[0]) and (self.start_pos[1] > self.end_pos[1]):
                print("Bottom Right")
                rect_start_point = [self.start_pos[0], self.end_pos[1]]
                rect_size = [abs(self.start_pos[0] - self.end_pos[0]), abs(self.start_pos[1] - self.end_pos[1])]

                print("Pos:", self.start_pos, "Size:", rect_size)
                Color(rgba=(23 / 255, 143 / 255, 54 / 255, 0.6))
                self.rect = Rectangle(pos=rect_start_point, size=(rect_size))

            elif (self.start_pos[0] > self.end_pos[0]) and (self.start_pos[1] < self.end_pos[1]):
                print("Top Left")
                rect_start_point = [self.end_pos[0], self.start_pos[1]]
                rect_size = [abs(self.start_pos[0] - self.end_pos[0]), abs(self.start_pos[1] - self.end_pos[1])]

                print("Pos:", self.start_pos, "Size:", rect_size)
                Color(rgba=(100 / 255, 93 / 255, 65 / 255, 0.6))
                self.rect = Rectangle(pos=rect_start_point, size=(rect_size))

            elif (self.start_pos[0] > self.end_pos[0]) and (self.start_pos[1] > self.end_pos[1]):
                print("Bottom Left")
                rect_start_point = self.end_pos
                rect_size = [abs(self.start_pos[0] - self.end_pos[0]), abs(self.start_pos[1] - self.end_pos[1])]

                print("Pos:", self.start_pos, "Size:", rect_size)
                Color(rgba=(100 / 255, 45 / 255, 34 / 255, 0.6))
                self.rect = Rectangle(pos=rect_start_point, size=(rect_size))

            else:
                print("Same Axis")


    def on_touch_up(self, touch):
        rect_size = [10, 10]
        with self.canvas:
            self.canvas.clear()
            # Load Image
            self.img = Image(source=self.img_path)
            self.img.allow_stretch = True
            self.img.keep_ratio = True
            self.img.size = self.size
            # Position set
            self.img.pos = (0, 0)
            self.img.opacity = 1

            self.end_pos = [touch.x, touch.y]
            print("End pos  :", self.end_pos)

            if self.start_pos == self.end_pos:
                print("Same position")

            elif (self.start_pos[0] < self.end_pos[0]) and (self.start_pos[1] < self.end_pos[1]):
                print("Top Right")
                rect_start_point = self.start_pos
                rect_size = [abs(self.start_pos[0] - self.end_pos[0]), abs(self.start_pos[1] - self.end_pos[1])]

                print("Pos:", self.start_pos, "Size:", rect_size)
                Color(rgba=(100 / 255, 143 / 255, 165 / 255, 0.6))
                self.rect = Rectangle(pos=rect_start_point, size=(rect_size))

            elif (self.start_pos[0] < self.end_pos[0]) and (self.start_pos[1] > self.end_pos[1]):
                print("Bottom Right")
                rect_start_point = [self.start_pos[0], self.end_pos[1]]
                rect_size = [abs(self.start_pos[0] - self.end_pos[0]), abs(self.start_pos[1] - self.end_pos[1])]

                print("Pos:", self.start_pos, "Size:", rect_size)
                Color(rgba=(23 / 255, 143 / 255, 54 / 255, 0.6))
                self.rect = Rectangle(pos=rect_start_point, size=(rect_size))

            elif (self.start_pos[0] > self.end_pos[0]) and (self.start_pos[1] < self.end_pos[1]):
                print("Top Left")
                rect_start_point = [self.end_pos[0], self.start_pos[1]]
                rect_size = [abs(self.start_pos[0] - self.end_pos[0]), abs(self.start_pos[1] - self.end_pos[1])]

                print("Pos:", self.start_pos, "Size:", rect_size)
                Color(rgba=(100 / 255, 93 / 255, 65 / 255, 0.6))
                self.rect = Rectangle(pos=rect_start_point, size=(rect_size))

            elif (self.start_pos[0] > self.end_pos[0]) and (self.start_pos[1] > self.end_pos[1]):
                print("Bottom Left")
                rect_start_point = self.end_pos
                rect_size = [abs(self.start_pos[0]-self.end_pos[0]), abs(self.start_pos[1]-self.end_pos[1])]

                print("Pos:", self.start_pos, "Size:", rect_size)
                Color(rgba=(100 / 255, 45 / 255, 34 / 255, 0.6))
                self.rect = Rectangle(pos=rect_start_point, size=(rect_size))

            else:
                print("Same Axis")

class TouchApp(App):
    def clear_canvas(self,obj):
        self.ROI.canvas.clear()

    def build(self):
        Parent = BoxLayout()
        self.ROI = TouchInput()
        Parent.add_widget(self.ROI)
        but = Button(text="clear", size_hint_x=0.2)
        but.bind(on_release=self.clear_canvas)
        Parent.add_widget(but)
        #self.load_kv("overlay.kv")

        return Parent

if __name__ == "__main__":
    TouchApp().run()

Заранее спасибо!