#!/usr/bin/env python3

# SàT: a XMPP client
# Copyright (C) 2009-2019 Jérôme Poisson (goffi@goffi.org)

# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.

# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Affero General Public License for more details.

# You should have received a copy of the GNU Affero General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

"""Misc utils for both backend and frontends"""


def per_luminance(red, green, blue):
    """Caculate the perceived luminance of a RGB color

    @param red(int): 0-1 normalized value of red
    @param green(int): 0-1 normalized value of green
    @param blue(int): 0-1 normalized value of blue
    @return (float): 0-1 value of luminance (<0.5 is dark, else it's light)
    """
    # cf. https://stackoverflow.com/a/1855903, thanks Gacek

    return 0.299 * red + 0.587 * green + 0.114 * blue