protected function renderImageByGD($code)
{
$image = imagecreatetruecolor($this->width, $this->height);
$backColor = imagecolorallocate($image, (int) ($this->backColor % 0x1000000 / 0x10000), (int) ($this->backColor % 0x10000 / 0x100), $this->backColor % 0x100);
imagefilledrectangle($image, 0, 0, $this->width - 1, $this->height - 1, $backColor);
imagecolordeallocate($image, $backColor);
if ($this->transparent) {
imagecolortransparent($image, $backColor);
}
$foreColor = imagecolorallocate($image, (int) ($this->foreColor % 0x1000000 / 0x10000), (int) ($this->foreColor % 0x10000 / 0x100), $this->foreColor % 0x100);
$length = strlen($code);
$box = imagettfbbox(30, 0, $this->fontFile, $code);
$w = $box[4] - $box[0] + $this->offset * ($length - 1);
$h = $box[1] - $box[5];
$scale = min(($this->width - $this->padding * 2) / $w, ($this->height - $this->padding * 2) / $h);
$x = 10;
$y = round($this->height * 27 / 40);
for ($i = 0; $i < $length; ++$i) {
$fontSize = (int) (rand(26, 32) * $scale * 0.8);
$angle = rand(-10, 10);
$letter = $code[$i];
$box = imagettftext($image, $fontSize, $angle, $x, $y, $foreColor, $this->fontFile, $letter);
$x = $box[2] + $this->offset;
}
imagecolordeallocate($image, $foreColor);
ob_start();
imagepng($image);
imagedestroy($image);
return ob_get_clean();
}