From DevShed today, there's a new tutorial on using the built-in PHP image manipulation functionality (the GD libraries) to dynamically put watermarks on your images.

PHP features a wide array of functions for image handling and manipulation. In today's article, we are going to use those functions to create an image watermarking class. This class will operate on two images: a source image and a watermark. As an optional third parameter our class will also accept an alpha value '" allowing our watermark to contain alpha transparency.

They start off with a brief summary of what the functions are and how the script will work. From there, it's all source code and examples to get the script up and working. In the end, you'll have a script you can call from an img tag in HTML and it will generate the content for you automatically...