xref: /webtrees/app/Statistics/Service/ColorService.php (revision 0c0910bf0f275a14f35d2ccdf698f91f79e269d4) 
1<?php
2
3/**
4 * webtrees: online genealogy
5 * Copyright (C) 2019 webtrees development team
6 * This program is free software: you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation, either version 3 of the License, or
9 * (at your option) any later version.
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
14 * You should have received a copy of the GNU General Public License
15 * along with this program. If not, see <http://www.gnu.org/licenses/>.
16 */
17declare(strict_types=1);
18
19namespace Fisharebest\Webtrees\Statistics\Service;
20
21/**
22 * Functions for managing and manipulating colors.
23 */
24class ColorService
25{
26    /**
27     * Interpolates the number of color steps between a given start and end color.
28     *
29     * @param string $startColor The start color
30     * @param string $endColor   The end color
31     * @param int    $steps      The number of steps to interpolate
32     *
33     * @return array
34     */
35    public function interpolateRgb(string $startColor, string $endColor, int $steps): array
36    {
37        if (!$steps) {
38            return [];
39        }
40
41        $s       = $this->hexToRgb($startColor);
42        $e       = $this->hexToRgb($endColor);
43        $colors  = [];
44        $factorR = ($e[0] - $s[0]) / $steps;
45        $factorG = ($e[1] - $s[1]) / $steps;
46        $factorB = ($e[2] - $s[2]) / $steps;
47
48        for ($x = 1; $x < $steps; ++$x) {
49            $colors[] = $this->rgbToHex(
50                (int) round($s[0] + ($factorR * $x)),
51                (int) round($s[1] + ($factorG * $x)),
52                (int) round($s[2] + ($factorB * $x))
53            );
54        }
55
56        $colors[] = $this->rgbToHex($e[0], $e[1], $e[2]);
57
58        return $colors;
59    }
60
61    /**
62     * Converts the color values to the HTML hex representation.
63     *
64     * @param int $r The red color value
65     * @param int $g The green color value
66     * @param int $b The blue color value
67     *
68     * @return string
69     */
70    private function rgbToHex(int $r, int $g, int $b): string
71    {
72        return sprintf('#%02x%02x%02x', $r, $g, $b);
73    }
74
75    /**
76     * Converts the HTML color hex representation to an array of color values.
77     *
78     * @param string $hex The HTML hex color code
79     *
80     * @return array
81     */
82    private function hexToRgb(string $hex): array
83    {
84        return array_map('hexdec', str_split(ltrim($hex, '#'), 2));
85    }
86}
87