Approximate color using a Delta E (CIE 1994) diff

diff --git a/wcfsetup/install/files/lib/system/html/input/node/HtmlInputNodeWoltlabColor.class.php b/wcfsetup/install/files/lib/system/html/input/node/HtmlInputNodeWoltlabColor.class.php
new file mode 100644 (file)
index 0000000..f0f0b64
--- /dev/null
+++ b/wcfsetup/install/files/lib/system/html/input/node/HtmlInputNodeWoltlabColor.class.php
@@ -0,0 +1,207 @@
+<?php
+namespace wcf\system\html\input\node;
+use wcf\data\bbcode\BBCodeCache;
+use wcf\system\bbcode\BBCodeHandler;
+use wcf\system\html\metacode\converter\IMetacodeConverter;
+use wcf\system\html\node\AbstractHtmlNodeProcessor;
+use wcf\util\DOMUtil;
+use wcf\util\StringUtil;
+
+/**
+ * Processes `<woltlab-color>` to check for valid color arguments.
+ *
+ * @author      Alexander Ebert
+ * @copyright   2001-2016 WoltLab GmbH
+ * @license     GNU Lesser General Public License <http://opensource.org/licenses/lgpl-license.php>
+ * @package     WoltLabSuite\Core\System\Html\Input\Node
+ * @since       3.0
+ */
+class HtmlInputNodeWoltlabColor extends AbstractHtmlInputNode {
+       /**
+        * @inheritDoc
+        */
+       protected $tagName = 'woltlab-color';
+       
+       public static $validColors = [
+               '000000', '000080', '0000CD', '0000FF', '006400', '008000', '008080', '00FF00',
+               '00FFFF', '2F4F4F', '40E0D0', '4B0082', '696969', '800000', '800080', '808080',
+               '8B4513', 'A52A2A', 'A9A9A9', 'ADD8E6', 'AFEEEE', 'B22222', 'D3D3D3', 'DAA520',
+               'DDA0DD', 'E6E6FA', 'EE82EE', 'F0F8FF', 'F0FFF0', 'F0FFFF', 'FAEBD7', 'FF0000',
+               'FF8C00', 'FFA07A', 'FFA500', 'FFD700', 'FFF0F5', 'FFFF00', 'FFFFE0', 'FFFFFF'
+       ];
+       
+       protected static $colorsToLab = [];
+       
+       /**
+        * @inheritDoc
+        */
+       public function isAllowed(AbstractHtmlNodeProcessor $htmlNodeProcessor) {
+               if (BBCodeHandler::getInstance()->isAvailableBBCode('color')) {
+                       return [];
+               }
+               
+               if (!$htmlNodeProcessor->getDocument()->getElementsByTagName('woltlab-color')->length) {
+                       return [];
+               }
+               
+               return ['color'];
+       }
+       
+       /**
+        * @inheritDoc
+        */
+       public function process(array $elements, AbstractHtmlNodeProcessor $htmlNodeProcessor) {
+               /** @var \DOMElement $element */
+               foreach ($elements as $element) {
+                       if (preg_match('~\bwoltlab-color-([a-z0-9]{6})\b~i', $element->getAttribute('class'), $matches)) {
+                               $color = strtoupper($matches[1]);
+                               if (!in_array($color, self::$validColors)) {
+                                       $color = $this->getClosestColor($color);
+                               }
+                               
+                               $element->setAttribute('class', 'woltlab-color-'.$color);
+                       }
+                       else {
+                               DOMUtil::removeNode($element, true);
+                       }
+               }
+       }
+       
+       protected function getClosestColor($hex) {
+               if (empty(self::$colorsToLab)) {
+                       // build static lookup table
+                       foreach (self::$validColors as $color) {
+                               self::$colorsToLab[$color] = $this->hexToLab($color);
+                       }
+               }
+               
+               $lab1 = $this->hexToLab($hex);
+               
+               $diff = 0;
+               $newColor = '';
+               
+               foreach (self::$colorsToLab as $color => $lab2) {
+                       $newDiff = $this->deltaE_cie1994($lab1, $lab2);
+                       
+                       if ($newColor === '' || $diff > $newDiff) {
+                               $diff = $newDiff;
+                               $newColor = $color;
+                       }
+               }
+               
+               return $newColor;
+       }
+       
+       protected function hexToLab($hex) {
+               return $this->xyzToLab(
+                       $this->rgbToXyz(
+                               $this->hexToRgb($hex)
+                       )
+               );
+       }
+       
+       protected function hexToRgb($hex) {
+               // [r, g, b]
+               return [
+                       hexdec($hex{0}.$hex{1}),
+                       hexdec($hex{2}.$hex{3}),
+                       hexdec($hex{4}.$hex{5})
+               ];
+       }
+       
+       protected function rgbToXyz($rgb) {
+               // convert into values between 0 and 1
+               $red = $rgb[0] / 255;
+               $green = $rgb[1] / 255;
+               $blue = $rgb[2] / 255;
+               
+               if ($red > 0.04045) {
+                       $red = ($red + 0.055) / 1.055;
+                       $red = pow($red, 2.4);
+               }
+               else {
+                       $red = $red / 12.92;
+               }
+               
+               if ($green > 0.04045) {
+                       $green = ($green + 0.055) / 1.055;
+                       $green = pow($green, 2.4);
+               }
+               else {
+                       $green = $green / 12.92;
+               }
+               
+               if ($blue > 0.04045) {
+                       $blue = ($blue + 0.055) / 1.055;
+                       $blue = pow($blue, 2.4);
+               }
+               else {
+                       $blue = $blue / 12.92;
+               }
+               
+               $red *= 100;
+               $green *= 100;
+               $blue *= 100;
+               
+               // [x, y, z]
+               return [
+                       $red * 0.4124 + $green * 0.3576 + $blue * 0.1805,
+                       $red * 0.2126 + $green * 0.7152 + $blue * 0.0722,
+                       $red * 0.0193 + $green * 0.1192 + $blue * 0.9505
+               ];
+       }
+       
+       protected function xyzToLab($xyz) {
+               $x = $xyz[0] / 95.047;
+               $y = $xyz[1] / 100;
+               $z = $xyz[2] / 108.883;
+               
+               if ($x > 0.008856) {
+                       $x = pow($x, 1 / 3);
+               }
+               else {
+                       $x = 7.787 * $x + 16 / 116;
+               }
+               
+               if ($y > 0.008856) {
+                       $y = pow($y, 1 / 3);
+               }
+               else {
+                       $y = (7.787 * $y) + (16 / 116);
+               }
+               
+               if ($z > 0.008856) {
+                       $z = pow($z, 1 / 3);
+               }
+               else {
+                       $z = 7.787 * $z + 16 / 116;
+               }
+               
+               // [l, a, b]
+               return [
+                       116 * $y - 16,
+                       500 * ($x - $y),
+                       200 * ($y - $z)
+               ];
+       }
+       
+       protected function deltaE_cie1994($lab1, $lab2) {
+               // Delta E (CIE 1994) difference of two colors
+               // http://www.brucelindbloom.com/index.html?Eqn_DeltaE_CIE94.html
+               $c1 = sqrt($lab1[1] * $lab1[1] + $lab1[2] * $lab1[2]);
+               $c2 = sqrt($lab2[1] * $lab2[1] + $lab2[2] * $lab2[2]);
+               
+               $dc = $c1 - $c2;
+               $dl = $lab1[0] - $lab2[0];
+               $da = $lab1[1] - $lab2[1];
+               $db = $lab1[2] - $lab2[2];
+               $dh = ($da * $da) + ($db * $db) - ($dc * $dc);
+               $dh = ($dh < 0) ? 0 : sqrt($dh);
+               
+               $first = $dl;
+               $second = $dc / (1 + 0.045 * $c1);
+               $third = $dh / (1 + 0.015 * $c1);
+               
+               return sqrt($first * $first + $second * $second + $third * $third);
+       }
+}