private function createFont()
{
$_tmp = $this->width / $this->len;
for ($_i = 0; $_i < $this->len; $_i++) {
$this->colorFont = imagecolorallocate($this->image, mt_rand(0, 140), mt_rand(0, 140), mt_rand(0, 140));
$this->colorShadow = imagecolorallocate($this->image, 255, 255, 255);
$_angle = mt_rand(-15, 15);
$_x = $_tmp * $_i + mt_rand(1, 5);
$_y = $this->height / 1.4;
imagettftext($this->image, $this->fontSize, $_angle, $_x + 1, $_y + 1, $this->colorShadow, $this->fontFile, $this->code[$_i]);
//投影
imagettftext($this->image, $this->fontSize, $_angle, $_x, $_y, $this->colorFont, $this->fontFile, $this->code[$_i]);
}
}