view sat/tools/common/ @ 3045:6af44ca3beac

tools (common): helping method to calculate luminance: - a new `utils` module has been added for backend and frontends generic utilities - per_luminance method calculate the perceived luminance of a colour (is it dark or light?). This is useful to automatically select the suitable colour in a theme.
author Goffi <>
date Tue, 01 Oct 2019 22:49:10 +0200
children 9d0df638c8b4
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#!/usr/bin/env python3

# SàT: a XMPP client
# Copyright (C) 2009-2019 Jérôme Poisson (

# 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
# 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 <>.

"""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., thanks Gacek

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