CRM/Utils/Color.php

   1 <?php
   2 /*
   3  +--------------------------------------------------------------------+
   4  | CiviCRM version 5                                                  |
   5  +--------------------------------------------------------------------+
   6  | Copyright CiviCRM LLC (c) 2004-2019                                |
   7  +--------------------------------------------------------------------+
   8  | This file is a part of CiviCRM.                                    |
   9  |                                                                    |
  10  | CiviCRM is free software; you can copy, modify, and distribute it  |
  11  | under the terms of the GNU Affero General Public License           |
  12  | Version 3, 19 November 2007 and the CiviCRM Licensing Exception.   |
  13  |                                                                    |
  14  | CiviCRM is distributed in the hope that it will be useful, but     |
  15  | WITHOUT ANY WARRANTY; without even the implied warranty of         |
  16  | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.               |
  17  | See the GNU Affero General Public License for more details.        |
  18  |                                                                    |
  19  | You should have received a copy of the GNU Affero General Public   |
  20  | License and the CiviCRM Licensing Exception along                  |
  21  | with this program; if not, contact CiviCRM LLC                     |
  22  | at info[AT]civicrm[DOT]org. If you have questions about the        |
  23  | GNU Affero General Public License or the licensing of CiviCRM,     |
  24  | see the CiviCRM license FAQ at http://civicrm.org/licensing        |
  25  +--------------------------------------------------------------------+
  26  */
  27
  28 /**
  29  *
  30  * @package CRM
  31  * @copyright CiviCRM LLC (c) 2004-2019
  32  */
  33
  34 /**
  35  * Static utility functions for working with colors
  36  */
  37 class CRM_Utils_Color {
  38
  39   /**
  40    * Determine the appropriate text color for a given background.
  41    *
  42    * Based on YIQ value.
  43    *
  44    * @param string $hexcolor
  45    * @param string $black
  46    * @param string $white
  47    * @return string
  48    */
  49   public static function getContrast($hexcolor, $black = 'black', $white = 'white') {
  50     list($r, $g, $b) = self::getRgb($hexcolor);
  51     $yiq = (($r * 299) + ($g * 587) + ($b * 114)) / 1000;
  52     return ($yiq >= 128) ? $black : $white;
  53   }
  54
  55   /**
  56    * Convert hex color to decimal
  57    *
  58    * @param string $hexcolor
  59    * @return array
  60    *   [red, green, blue]
  61    */
  62   public static function getRgb($hexcolor) {
  63     $hexcolor = trim($hexcolor, ' #');
  64     if (strlen($hexcolor) === 3) {
  65       $hexcolor = $hexcolor[0] . $hexcolor[0] . $hexcolor[1] . $hexcolor[1] . $hexcolor[2] . $hexcolor[2];
  66     }
  67     return [
  68       hexdec(substr($hexcolor, 0, 2)),
  69       hexdec(substr($hexcolor, 2, 2)),
  70       hexdec(substr($hexcolor, 4, 2)),
  71     ];
  72   }
  73
  74   /**
  75    * Calculate a highlight color from a base color
  76    *
  77    * @param $hexcolor
  78    * @return string
  79    */
  80   public static function getHighlight($hexcolor) {
  81     $rgb = CRM_Utils_Color::getRgb($hexcolor);
  82     $avg = array_sum($rgb) / 3;
  83     foreach ($rgb as &$v) {
  84       if ($avg > 242) {
  85         // For very bright values, lower the brightness
  86         $v -= 50;
  87       }
  88       else {
  89         // Bump up brightness on a nonlinear curve - darker colors get more of a boost
  90         $v = min(255, intval((-.0035 * ($v - 242) ** 2) + 260));
  91       }
  92     }
  93     return '#' . implode(array_map('dechex', $rgb));
  94   }
  95
  96 }