xref: /webtrees/app/Statistics/Service/ColorService.php (revision da7f6dd728aff7a0c0b922f5fd8849698cf0456d) 
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 */
17
18declare(strict_types=1);
19
20namespace Fisharebest\Webtrees\Statistics\Service;
21
22/**
23 * Functions for managing and manipulating colors.
24 */
25class ColorService
26{
27    /**
28     * Interpolates the number of color steps between a given start and end color.
29     *
30     * @param string $startColor The start color
31     * @param string $endColor   The end color
32     * @param int    $steps      The number of steps to interpolate
33     *
34     * @return array
35     */
36    public function interpolateRgb(string $startColor, string $endColor, int $steps): array
37    {
38        if (!$steps) {
39            return [];
40        }
41
42        $s       = $this->hexToRgb($startColor);
43        $e       = $this->hexToRgb($endColor);
44        $colors  = [];
45        $factorR = ($e[0] - $s[0]) / $steps;
46        $factorG = ($e[1] - $s[1]) / $steps;
47        $factorB = ($e[2] - $s[2]) / $steps;
48
49        for ($x = 1; $x < $steps; ++$x) {
50            $colors[] = $this->rgbToHex(
51                (int) round($s[0] + ($factorR * $x)),
52                (int) round($s[1] + ($factorG * $x)),
53                (int) round($s[2] + ($factorB * $x))
54            );
55        }
56
57        $colors[] = $this->rgbToHex($e[0], $e[1], $e[2]);
58
59        return $colors;
60    }
61
62    /**
63     * Converts the color values to the HTML hex representation.
64     *
65     * @param int $r The red color value
66     * @param int $g The green color value
67     * @param int $b The blue color value
68     *
69     * @return string
70     */
71    private function rgbToHex(int $r, int $g, int $b): string
72    {
73        return sprintf('#%02x%02x%02x', $r, $g, $b);
74    }
75
76    /**
77     * Converts the HTML color hex representation to an array of color values.
78     *
79     * @param string $hex The HTML hex color code
80     *
81     * @return array
82     */
83    private function hexToRgb(string $hex): array
84    {
85        return array_map('hexdec', str_split(ltrim($hex, '#'), 2));
86    }
87}
88