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annotate sat/tools/common/utils.py @ 3045:6af44ca3beac

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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 <goffi@goffi.org>
date Tue, 01 Oct 2019 22:49:10 +0200
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children 9d0df638c8b4
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
3045
6af44ca3beac tools (common): helping method to calculate luminance:
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1 #!/usr/bin/env python3
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2
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3 # SàT: a XMPP client
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4 # Copyright (C) 2009-2019 Jérôme Poisson (goffi@goffi.org)
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5
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6 # This program is free software: you can redistribute it and/or modify
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7 # it under the terms of the GNU Affero General Public License as published by
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8 # the Free Software Foundation, either version 3 of the License, or
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9 # (at your option) any later version.
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10
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11 # This program is distributed in the hope that it will be useful,
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12 # but WITHOUT ANY WARRANTY; without even the implied warranty of
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13 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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14 # GNU Affero General Public License for more details.
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16 # You should have received a copy of the GNU Affero General Public License
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17 # along with this program. If not, see <http://www.gnu.org/licenses/>.
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18
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19 """Misc utils for both backend and frontends"""
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22 def per_luminance(red, green, blue):
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23 """Caculate the perceived luminance of a RGB color
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24
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25 @param red(int): 0-1 normalized value of red
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26 @param green(int): 0-1 normalized value of green
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27 @param blue(int): 0-1 normalized value of blue
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28 @return (float): 0-1 value of luminance (<0.5 is dark, else it's light)
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29 """
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30 # cf. https://stackoverflow.com/a/1855903, thanks Gacek
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31
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32 return 0.299 * red + 0.587 * green + 0.114 * blue