Image scatter that collide on white color of (can be changed for opaque)

imgscatter.py

from kivy.lang import Builder
from kivy.factory import Factory as F
from kivy.properties import StringProperty, ObjectProperty, BooleanProperty
from kivy.core.image import Image as CoreImage

Builder.load_string("""
<ImgScatter>:
    size_hint: None, None
    canvas:
        Color:
            rgba: 1, 1, 1, 1
        Rectangle:
            size: self.size
            texture: self.texture
""")

class ImgScatter(F.Scatter):
    source = StringProperty()
    texture = ObjectProperty(None, allownone=True)
    is_touch_down_collide = BooleanProperty(False)

    def on_source(self, *largs):
        self.img = img = CoreImage(self.source, keep_data=True)
        self.texture = img.texture
        self.size = img.texture.size
        self.is_touch_down_collide = False

    def collide_point(self, x, y):
        if not self.is_touch_down_collide:
            # default collide_point
            return super(ImgScatter, self).collide_point(x, y)

        lx, ly = self.to_local(x, y)
        if lx < 0 or lx > self.width:
            return False
        if ly < 0 or ly > self.height:
            return False
        lx /= float(self.width)
        ly /= float(self.height)

        cx = int(lx * self.texture.size[0])
        cy = int((1 - ly) * self.texture.size[1])
        color = self.img.read_pixel(cx, cy)

        # test alpha ?
        # return color[-1] > 0
        return color == [1, 1, 1, 1]

    def on_touch_down(self, touch):
        try:
            self.is_touch_down_collide = True
            return super(ImgScatter, self).on_touch_down(touch)
        finally:
            self.is_touch_down_collide = False


if __name__ == "__main__":
    from kivy.app import App
    import sys

    assert(len(sys.argv[1:]) >= 1)

    class TestImgScatter(App):
        def build(self):
            self.root = F.FloatLayout()
            for source in sys.argv[1:]:
                self.root.add_widget(
                    ImgScatter(source=source)
                )

    TestImgScatter().run()