overlay.py

import gi
gi.require_version('Gtk', '3.0')
from gi.repository import Gtk, Gdk, GObject, GLib
import cairo
import math

import io
import PIL.Image as Image

import random

window = Gtk.Window()
window.set_position(Gtk.WindowPosition.CENTER)
window.set_default_size(400, 550)
window.set_title("Zongus")
window.connect("delete-event", Gtk.main_quit)

window.set_decorated(True)

# The magic lines
window.set_app_paintable(True)
window.set_visual(window.get_screen().get_rgba_visual())


draw = None


def clear(_w, cr):

    print("clear")


    cr.set_source_rgba(0, 0, 0, 0)
    cr.rectangle(0, 0, 1000, 1000)
    cr.fill()


    global draw
    draw = paint
    window.queue_draw()


def paint(_w, cr):

    print("paint")


    win = Gdk.get_default_root_window()
    x0, y0 = window.get_position()
    dx, dy = window.get_size()
    y0 += 37  # title bar -- FIXME

    pixbuf = Gdk.pixbuf_get_from_window(win, x0, y0, dx, dy)
    _, bytearr = pixbuf.save_to_bufferv('png', [], [])
    img = Image.open(io.BytesIO(bytearr))


    cr.set_source_rgb(255, 0, 0)
    cr.set_line_width(1)
    def px_draw(x, y):
        cr.move_to(x, y)
        cr.line_to(x + 1, y + 1)
        cr.stroke()

    for idx, (h, s, v) in enumerate(img.convert('HSV').getdata()):
        x = idx % img.width
        y = idx // img.width
        if v / 255 < .5:  #.01
            px_draw(x, y)


    global draw
    draw = clear
    def redraw(): window.queue_draw(); return False
    GLib.timeout_add_seconds(4, redraw)


draw = clear


canv = Gtk.DrawingArea()
canv.connect('draw', lambda *args: draw(*args));
window.add(canv)

window.show_all()
Gtk.main()