public function createFromFile($filename)
    {
        $img = imagecreatefromstring(file_get_contents($filename));
        list($width, $height) = getimagesize($filename);

        $ascii = null;
        $incY = $this->scale;
        $incX = $this->scale / 2;
        
        for ($y = 0; $y < $height - 1; $y += $incY) {
            for ($x = 0; $x < $width - 1; $x += $incX) {
                $toX = min($x + $this->scale / 2, $width - 1);
                $toY = min($y + $this->scale, $height - 1);
                $luminance = $this->luminanceAreaAverage($img, $x, $y, $toX, $toY);
                $ascii .= $this->luminance2character($luminance);
            }
            $ascii .= PHP_EOL;
        }

        return $ascii;
    }