Php. Как вставить фото в генератор?

<?php
error_reporting(0);
$key = $_GET['q'];
if ($key == '') {
//$key = urlencode('test');
//print ' ';
}
?>
<?php
$q2 = $key;
$q2s = str_replace('+', ' ', $q2s);
session_start();
//You can do any necessary settings as you wish here
//If you reduce the width and height of the captcha here then you have to change it in the css file as well
$image_width = 600;
$image_height = 500;
$characters_on_image = 10;
$font = 'images/monofont.ttf';
//The characters that can be used in the CAPTCHA code. Avoid confusing characters (l 1 and i for example)
$possible_letters = "".$key."";
$random_dots = 0;
$random_lines = 20;
$random_imgs = 1;
$captcha_text_color="0x142864";
$captcha_noice_color = "0x142864";
$code = '';
$code = $key;
//$i = 0;
//while ($i < $characters_on_image)
//{
//    $code .= substr($possible_letters, mt_rand(0, strlen($possible_letters)-1), 1);
//    $i++;
//}
$font_size = $image_height * 0.04;
$image = @imagecreate($image_width, $image_height);

/*Setting the background, text and noise colours here */
$background_color = imagecolorallocate($image, 255, 255, 255);
$arr_text_color = RGB_HEX($captcha_text_color);
$text_color = imagecolorallocate($image, $arr_text_color['red'],
$arr_text_color['green'], $arr_text_color['blue']);
$arr_noice_color = RGB_HEX($captcha_noice_color);
$image_noise_color = imagecolorallocate($image, $arr_noice_color['red'],
$arr_noice_color['green'], $arr_noice_color['blue']);
/*This generates the dots randomly strings in background */
for( $i=0; $i<$random_dots; $i++ )
{
    imagefilledellipse($image, mt_rand(0,$image_width),
     mt_rand(0,$image_height), 2, 3, $image_noise_color);
}

for( $i=0; $i<$random_imgs; $i++ )
{
$green = imagecolorallocate($image, 0, 255, 0);

imageellipse($image, 250, 250, 300, 200, $green);

}
/*This generates lines randomly strings in background of image */
for( $i=0; $i<$random_lines; $i++ )
{
    imageline($image, mt_rand(0,$image_width), mt_rand(0,$image_height),
     mt_rand(0,$image_width), mt_rand(0,$image_height), $image_noise_color);
}
/*This creates a text box and add 6 letters code in it */
$textbox = imagettfbbox($font_size, 0, $font, $code);
$x = ($image_width - $textbox[4])/10;
$y = ($image_height - $textbox[5])/10;
imagettftext($image, $font_size, 0, $x, $y, $text_color, $font , $code);
/* Show captcha image in the page html page */
header('Content-Type: image/jpeg');// defining the image type to be shown in browser widow
imagejpeg($image);//showing the image
imagedestroy($image);//destroying the image instance
$_SESSION['vpb_captcha_code'] = $code;
function RGB_HEX ($hexstr)
{
    $int = hexdec($hexstr);
    return array("red" => 0xFF & ($int >> 0x10),"green" => 0xFF & ($int >> 0x8),"blue" => 0xFF & $int);
}
?>

Получается так

P.S. Хочу чтобы за место круга грузилось рандомное фото из папки. Пожалуйста помогите реализовать - очень надо.