Samples a color from the screen and prints the hex value to the terminal.

color_picker.py

# Samples a color from the screen and prints the hex value to the terminal.
# Usage: `python color_picker.py` and then click somewhere to sample.

from gi import require_version

require_version('Gdk', '3.0')
require_version('Gtk', '3.0')

from gi.repository import Gdk
from gi.repository import Gtk

import sys


def get_hex_color(window, x, y):
    pixbuf = Gdk.pixbuf_get_from_window(window, x, y, 1, 1)
    rgb = pixbuf.get_pixels()
    return tuple(map(int, rgb))


def event_handler(event, window, _):
    if event.type == Gdk.EventType.BUTTON_RELEASE:
        # Strictly speaking this isn't necessary since the program is about to
        # exit, but I've included it for the sake of completeness.
        Gdk.pointer_ungrab(Gdk.CURRENT_TIME)

        _, x, y = event.get_coords()

        # Understanding this is left as an exercise for the reader.
        print('#%02x%02x%02x' % get_hex_color(window, x, y))

        sys.exit(0)


if __name__ == '__main__':
    window = Gdk.get_default_root_window()

    Gdk.event_handler_set(event_handler, window, None)

    # This changes the cursor and makes it so clicks won't register on other
    # windows and change focus.
    Gdk.pointer_grab(
        window,
        False,
        Gdk.EventMask.ALL_EVENTS_MASK,
        None,
        # Not the best cursor, but I needed something to differentiate from
        # the system default.
        Gdk.Cursor(Gdk.CursorType.CROSSHAIR),
        Gdk.CURRENT_TIME,
    )

    # TODO: Should probably grab the keyboard too so the user can't alt-tab
    # and get into an odd state.

    Gtk.main()