i dont think php can actually do this automatically by itself. I think you would have to use a 3rd party application which of course would have to be installed onto the server.
You can create thumbnails watermarks etc using PHP. The GDlib library has all the features you need. There are also classes available (free) for this purpose.
True, i need to make images of a website, interesting site CoderChat but couldn't find what i needed, i guess i'll use an external website to provide me this service