Added letter based avatar provider

app/User/Avatar/GravatarProvider.php

@@ -5,6 +5,12 @@ namespace Kanboard\User\Avatar;
 use Kanboard\Core\Base;
 use Kanboard\Core\User\Avatar\AvatarProviderInterface;
 
+/**
+ * Gravatar Avatar Provider
+ *
+ * @package  avatar
+ * @author   Frederic Guillot
+ */
 class GravatarProvider extends Base implements AvatarProviderInterface
 {
     /**

app/User/Avatar/LetterAvatarProvider.php

@@ -0,0 +1,169 @@
+<?php
+
+namespace Kanboard\User\Avatar;
+
+use Kanboard\Core\Base;
+use Kanboard\Core\User\Avatar\AvatarProviderInterface;
+
+/**
+ * Letter Avatar Provider
+ *
+ * The color hash algorithm is backported from the Javascript library color-hash
+ * Source: https://github.com/zenozeng/color-hash
+ * Author: Zeno Zeng (MIT License)
+ *
+ * @package  avatar
+ * @author   Frederic Guillot
+ */
+class LetterAvatarProvider extends Base implements AvatarProviderInterface
+{
+    protected $lightness = array(0.35, 0.5, 0.65);
+    protected $saturation = array(0.35, 0.5, 0.65);
+
+    /**
+     * Render avatar html
+     *
+     * @access public
+     * @param array $user
+     * @param int   $size
+     */
+    public function render(array $user, $size)
+    {
+        $initials = $this->helper->user->getInitials($user['name'] ?: $user['username']);
+        $rgb = $this->getBackgroundColor($initials);
+
+        return sprintf(
+            '<div class="avatar-letter" style="background-color: rgb(%d, %d, %d)" title="%s">%s</div>',
+            $rgb[0],
+            $rgb[1],
+            $rgb[2],
+            $this->helper->text->e($user['name'] ?: $user['username']),
+            $initials
+        );
+    }
+
+    /**
+     * Determine if the provider is active
+     *
+     * @access public
+     * @param  array $user
+     * @return boolean
+     */
+    public function isActive(array $user)
+    {
+        return true;
+    }
+
+    /**
+     * Get background color based on a string
+     *
+     * @param  string $str
+     * @return array
+     */
+    public function getBackgroundColor($str)
+    {
+        $hsl = $this->getHSL($str);
+        return $this->getRGB($hsl[0], $hsl[1], $hsl[2]);
+    }
+
+    /**
+     * Convert HSL to RGB
+     *
+     * @access protected
+     * @param  integer  $hue         Hue ∈ [0, 360)
+     * @param  integer  $saturation  Saturation ∈ [0, 1]
+     * @param  integer  $lightness   Lightness ∈ [0, 1]
+     * @return array
+     */
+    protected function getRGB($hue, $saturation, $lightness)
+    {
+        $hue /= 360;
+        $q = $lightness < 0.5 ? $lightness * (1 + $saturation) : $lightness + $saturation - $lightness * $saturation;
+        $p = 2 * $lightness - $q;
+
+        return array_map(function ($color) use ($q, $p) {
+            if ($color < 0) {
+                $color++;
+            }
+
+            if ($color > 1) {
+                $color--;
+            }
+
+            if ($color < 1/6) {
+                $color = $p + ($q - $p) * 6 * $color;
+            } else if ($color < 0.5) {
+                $color = $q;
+            } else if ($color < 2/3) {
+                $color = $p + ($q - $p) * 6 * (2/3 - $color);
+            } else {
+                $color = $p;
+            }
+
+            return round($color * 255);
+        }, array($hue + 1/3, $hue, $hue - 1/3));
+    }
+
+    /**
+     * Returns the hash in [h, s, l].
+     * Note that H ∈ [0, 360); S ∈ [0, 1]; L ∈ [0, 1];
+     *
+     * @access protected
+     * @param  string $str
+     * @return int[]
+     */
+    protected function getHSL($str)
+    {
+        $hash = $this->hash($str);
+        $hue = $hash % 359;
+
+        $hash = intval($hash / 360);
+        $saturation = $this->saturation[$hash % count($this->saturation)];
+
+        $hash = intval($hash / count($this->saturation));
+        $lightness = $this->lightness[$hash % count($this->lightness)];
+
+        return array($hue, $saturation, $lightness);
+    }
+
+    /**
+     * BKDR Hash (modified version)
+     *
+     * @access protected
+     * @param  string $str
+     * @return integer
+     */
+    protected function hash($str)
+    {
+        $seed = 131;
+        $seed2 = 137;
+        $hash = 0;
+
+        // Make hash more sensitive for short string like 'a', 'b', 'c'
+        $str .= 'x';
+        $max = intval(9007199254740991 / $seed2);
+
+        for ($i = 0, $ilen = mb_strlen($str); $i < $ilen; $i++) {
+            if ($hash > $max) {
+                $hash = intval($hash / $seed2);
+            }
+
+            $hash = $hash * $seed + $this->getCharCode($str[$i]);
+        }
+
+        return $hash;
+    }
+
+    /**
+     * Backport of Javascript function charCodeAt()
+     *
+     * @access protected
+     * @param  string $c
+     * @return integer
+     */
+    protected function getCharCode($c)
+    {
+        list(, $ord) = unpack('N', mb_convert_encoding($c, 'UCS-4BE', 'UTF-8'));
+        return $ord;
+    }
+}