Kohana 3.1 create imagejpeg or imagepng captcha - captcha

Question

Im trying to put a simple captcha in kohana 3.1 using the following code to generate for me the image from a model.
$session = Session::instance();
$string = '';
for ($i = 0; $i < 5; $i++) {
$string .= chr(rand(97, 122));
}
$cns_captcha = $session->set('random_number', $string);
$dir = LIBPATH.'fonts/';
$image = imagecreatetruecolor(165, 50);
// random number 1 or 2
$num = rand(1,2);
if($num==1)
{
$font = "Capture it 2.ttf"; // font style
}
else
{
$font = "Molot.otf";// font style
}
// random number 1 or 2
$num2 = rand(1,2);
if($num2==1)
{
$color = imagecolorallocate($image, 113, 193, 217);// color
}
else
{
$color = imagecolorallocate($image, 163, 197, 82);// color
}
$white = imagecolorallocate($image, 255, 255, 255); // background color white
imagefilledrectangle($image,0,0,399,99,$white);
imagettftext ($image, 30, 0, 10, 40, $color, $dir.$font, $cns_captcha);
//header('Content-Type: image/PNG');
imagepng($image);
unfortunately this is producing
�PNG IHDR�2�*�v�IDATx���o�d���4��4oM�Ѵe�&�)�F��NCCB���� � q�i�� qp��6M�0�S�/����]����ͱ�C�4t��؎�D��d�y��_?�����G�x�À��
and no image
thanks in advance for your assistance.

Answer 1

You dont set the content type, your browser assumes it is text.
imagettftext ($image, 30, 0, 10, 40, $color, $dir.$font, $cns_captcha);
$this->response->headers('Content-Type', 'image/png');
imagepng($image);
EDIT:
as a sidenote, have you looked at Kohana's image module? http://kohanaframework.org/3.3/guide-api/Image