Watermark Your Images with another Image Using PHP and GD Library
This code sample includes functions that use GD library to watermark images on the fly. The watermark is generated by overlaying the original image with another image, preferably a transparent PNG image.
The article along with complete code demonstrates the use of GD library to watermark images on the fly. The method demonstrated here to watermark an uploaded image is to overlay the original image with another image, preferably a transparent PNG image.