Many features that you see on the web require that the GD library be enabled on your PHP server. You may need the GD library if you are
attempting to display CAPTCHA graphics somewhere on your site.
In a default PHP installation, the GD library should already be enabled.
The following tutorial explains how to determine if the GD library is enabled on your PHP server, and how you might be able to turn this on.
You can check to see if the GD library is enabled by creating a simple phpinfo page on your web server.
Below are a few common examples on how to install GD.
Windows Server users
Ubuntu Linux users
sudo apt-get install php5-gd
Mac OSX users
For Mac OSX users, there is not a simple solution for enabling the GD library after PHP installation is complete. Instead, we recommend that you use MAMP, which you can obtain from the following location.
MAMP allows you to install Apache, MySQL and PHP for testing your websites locally.