test_blur.py

from kivy.clock import Clock
from kivy.app import App
from kivy.animation import Animation
from kivy.uix.widget import Widget
from kivy.uix.floatlayout import FloatLayout
from kivy.lang import Builder
from kivy.core.window import Window
from kivy.graphics import RenderContext
from kivy.uix.modalview import ModalView
from kivy.properties import ListProperty, NumericProperty, ObjectProperty, ColorProperty
from kivy.uix.effectwidget import EffectWidget, HorizontalBlurEffect, VerticalBlurEffect

shader = '''
$HEADER$

uniform vec2 resolution;
uniform float radius;

void main(void) {
    // need radius to be an int to iterate on it in the loops
    int int_radius = int(radius);
    gl_FragColor = vec4(0.);
    if (int_radius > 0) {
        for (int dx = -int_radius; dx < int_radius; dx++)
            for (int dy = -int_radius; dy < int_radius; dy++)
                gl_FragColor += texture2D(texture0, tex_coord0 + vec2(float(dx), float(dy)) / resolution);

        gl_FragColor /= float(4 * int_radius * int_radius);
    } else {
        gl_FragColor = texture2D(texture0, tex_coord0);
    }
}
'''

kv = """
#:import Factory kivy.factory.Factory

<BlurredModalView>:
    size_hint: .5, .5
    background_color: "#22222288"
    overlay_color: "#11111122"

    canvas.before:
        Color:
            rgba: self.overlay_color
        Rectangle:
            size: app.root.size
        Color:
            rgba: self.background_color
        Rectangle:
            pos: self.pos
            size: self.size

    Label:
        text: "This is in the modal"

FloatLayout:
    Blur:
        id: blur
        blur_radius: 0
        Image:
            source: "image.jpg"
        BoxLayout:
            size_hint: None, None
            pos_hint: {'center': (.5, .5)}
            orientation: 'vertical'
            size: self.minimum_size
            Button:
                size_hint: None, None
                text: 'press me'
                on_release: Factory.BlurredModalView(target=blur).open()
            Label:
                text: 'test'
                size_hint: None, None
"""


class Blur(EffectWidget):
    blur_radius = NumericProperty(0)
    blur_target_radius = NumericProperty(5)

    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        self._hblur = HorizontalBlurEffect(size=0)
        self._vblur = VerticalBlurEffect(size=0)
        self.effects = [
            self._hblur,
            self._vblur,
        ]

    def on_blur_radius(self, *args):
        self._hblur.size = self._vblur = self.blur_radius

    def blur(self):
        Animation.cancel_all(self, "blur_radius")
        Animation(blur_radius=self.blur_target_radius, d=1).start(self)

    def unblur(self):
        Animation.cancel_all(self, "blur_radius")
        Animation(blur_radius=0, d=.1).start(self)


class BlurredModalView(ModalView):
    background_color = ColorProperty([0, 0, 0, 0])
    overlay_color = ColorProperty([0, 0, 0, 0])
    target = ObjectProperty()

    def on_open(self):
        super().on_open()
        if self.target:
            self.target.blur()

    def on_dismiss(self):
        super().on_dismiss()
        if self.target:
            self.target.unblur()


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


if __name__ == '__main__':
    BluredApp().run()