Fix drawPolygon method

Author: DantSu

src/Image.php

@@ -961,8 +961,13 @@ public function drawPolygon(array $points, string $color = '#000000', $antialias
             \imageantialias($this->image, true);
             \imagepolygon($this->image, $points, \count($points) / 2, $color);
         }
+
         \imagefilledpolygon($this->image, $points, \count($points) / 2, $color);
 
+        if($antialias) {
+            \imageantialias($this->image, false);
+        }
+
         return $this;
     }