PHP dynamic image generation

One of the coolest things about PHP is its ability to create and manipulate images, and even output image streams directly to a browser using the GD library. You can take advantage of all the PHP image functions assuming your install of PHP was compiled with the GD library. For all the details and requirements just check out the GD section of PHP.net. I found this simple and entertaining little tutorial at PHPFreaks detailing how to dynamically create an image with text on it using a PHP script and outputting it to a browser - essentially what captcha does. The image functions are also useful for adding watermarks to images, resizing/cropping images, etc.