Add support for transparent color keyword

fixes #103

Author: bsweeney

src/Svg/Style.php

@@ -219,6 +219,10 @@ static function parseColor($color)
             return "currentcolor";
         }
 
+        if ($color === "transparent") {
+            return [0,0,0,0];
+        }
+
         // SVG color name
         if (isset(self::$colorNames[$color])) {
             return self::parseHexColor(self::$colorNames[$color]);

tests/Svg/StyleTest.php

@@ -18,6 +18,7 @@ public function test_parseColor()
     {
         $this->assertEquals("none", Style::parseColor("none"));
         $this->assertEquals("currentcolor", Style::parseColor("currentcolor"));
+        $this->assertEquals(array(0, 0, 0, 0), Style::parseColor("transparent"));
         $this->assertEquals(array(255, 0, 0, 1), Style::parseColor("RED"));
         $this->assertEquals(array(0, 0, 255, 1), Style::parseColor("blue"));
         $this->assertEquals(array(0, 0, 0, 1), Style::parseColor("black"));