gistfile1.txt

from kivy.lang import Builder
from kivy.base import runTouchApp
from kivy.uix.image import Image
from kivy.uix.gridlayout import GridLayout
from kivy.clock import Clock

class SizeImage(Image):
    pass

class ImagesGrid(GridLayout):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)

        self.bind(minimum_width=self.set_width,
                  width=self.set_width,
                  height=self.set_width,
                  children=self.set_width)

    def set_width(self, instance, value):
        self.width = len(self.children) * (680 / 1000) * self.height

root = Builder.load_string("""
<SizeImage>:
    allow_stretch: True
    keep_ratio: True

AnchorLayout:
    ScrollView:
        size_hint_x: None
        width: min(root.width, image_grid.width)
        ImagesGrid:
            id: image_grid
            rows: 1
            size_hint_x: None
""")

for i in range(5):
    root.ids.image_grid.add_widget(SizeImage(source="beauty.jpg"))

runTouchApp(root)