nextcloud/apps/theming/lib/util.php

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<?php
/**
* @copyright Copyright (c) 2016 Julius Härtl <jus@bitgrid.net>
*
* @license GNU AGPL version 3 or any later version
*
* 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/>.
*
*/
namespace OCA\Theming;
class Util {
/**
* @param string $color rgb color value
* @return bool
*/
public static function invertTextColor($color) {
$l = self::calculateLuminance($color);
if($l>0.5) {
return true;
} else {
return false;
}
}
/**
* @param string $color rgb color value
* @return float
*/
public static function calculateLuminance($color) {
$hex = preg_replace("/[^0-9A-Fa-f]/", '', $color);
if (strlen($hex) === 3) {
$hex = $hex{0} . $hex{0} . $hex{1} . $hex{1} . $hex{2} . $hex{2};
}
if (strlen($hex) !== 6) {
return 0;
}
$r = hexdec(substr($hex, 0, 2));
$g = hexdec(substr($hex, 2, 2));
$b = hexdec(substr($hex, 4, 2));
return (0.299 * $r + 0.587 * $g + 0.114 * $b)/255;
}
}