General Support: Captcha?

Is there anybody who has a captcha script and knows how to implement it into plogger.
This damn spammer keeps spamming me daily and it's become very annoying.

<?php
session_start();

$alphanum = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";

$rand = substr(str_shuffle($alphanum), 0, 5);

// Choose one of five background images
$bgNum = rand(1, 5);

// Create them yourself ;)
$image = imagecreatefromjpeg($_SERVER['DOCUMENT_ROOT']."/images/image_verification_background_$bgNum.jpg");

$textColor = imagecolorallocate ($image, 0, 0, 0);

imagestring ($image, 5, 8, 5, $rand, $textColor);

$_SESSION['captcha_code'] = md5($rand);

header("Expires: Mon, 26 Jul 1997 05:00:00 GMT");
header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT");
header("Cache-Control: no-store, no-cache, must-revalidate");
header("Cache-Control: post-check=0, pre-check=0", false);
header("Pragma: no-cache");
header('Content-type: image/jpeg');

imagejpeg($image);
imagedestroy($image);
?>

It could maybe be done better .. i run this for now .. maybe recode this later

just noticed that this was already in there

// If the captcha is required, check it here
if ($_SESSION['require_captcha'] == true) {
if (($_POST['captcha'] != $_SESSION['captcha']) || !$_POST['captcha']) {
$_SESSION["comment_post_error"] = "CAPTCHA check failed!";
header("Location: $redirect");
exit;
}
}

Does this mean that plogger has captcha already built in?


Also I'm not to sure which line to insert your scripts?

I added

<p>
<img src="'.$config["gallery_url"].'plog-captcha.php" alt="CAPTCHA Image" id="captcha-image" />
</p>
<p>
<input type="text" name="captcha" id="captcha" value="" size="28" tabindex="3" />
<label for="url">What does this say?</label>
</p>

to the comments section with the call function and it's working now :D

Hi Guys, I know this is old, but it seems to have worked for you both.

I followed what you have both said and I can't get it to work.

The image shows up and everything, but regardless of wether a code is entered, and regardless of if it is correct of not, the comment still goes for moderation.
If moderation is disabled, the comment is posted as normal.

Help!

SOVED:
in the file plog-functions.php you must fine the code (at line 1218):

$_SESSION['require_captcha'] = false;

and delete it and paste this:

$_SESSION['require_captcha'] = true;

Then in "comments.php" of your theme paste this before your "Post Comment" button:

<p>
<img src="'.$config["gallery_url"].'plog-captcha.php" alt="CAPTCHA Image" id="captcha-image" />
</p>
<p>
<input type="text" name="captcha" id="captcha" value="" size="28" tabindex="3" />
<label for="url">What does this say?</label>
</p>

Galerio: I have just tried this, there are actually two instances of 'require_captcha' I have set both to true, and copied your code exactly.
Is there anything else that you have done because I am obviously doing something wrong, it is still doing the same as it was.

Thanks for your help so far!