catcha

Catch-a spammer with a CAPTCHA.

Copyright (C) 2013 J.M. me@mynetx.net

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program. If not, see http://www.gnu.org/licenses/.

Please enable the GD extension in your PHP environment.

Getting started

1. Generate a challenge

require_once 'catcha.php';

$catcha = new Catcha;
$catcha->outputImage();

1. Store the Catcha object

$_SESSION['catcha'] = $catcha;

1. After the user enters the solution, restore the object

$catcha = $_SESSION['catcha'];

1. Check if the entered result was correct

$entered_result = -1;
if (isset($_POST['your_field_name'])) {
    $entered_result = intval($_POST['your_field_name']);
}
$catcha_solved = $catcha->isCorrectResult($entered_result);

Adapting to your needs

Set a custom challenge canvas image size

The canvas size defaults to 100 x 25 pixels. Customize the size:

$catcha->setImageSize($desired_width, $desired_height);

Use a custom font

By default, Catcha uses the Averia Light font licensed under the SIL
Open Font License Version 1.1 (http://scripts.sil.org/OFL).
You may as well use a custom True Type font (*.ttf):

$catcha->setImageFont($path_to_font);

Paint the canvas in a different color

The supported color codes include (upper- and lower case)

• ffff00

• ffff00
• ff0

$catcha->setImageColorBackground('#ffff00');

Write the equation in a different color

$catcha->setImageColorForeground('#ff0000');

Generate a new challenge and discard the old one

$catcha->newChallenge();

Get raw image data without sending to browser

The raw image data are in binary JPEG format, quality 80.

$image_data = $catcha->getImage();