Website crawler auto image downloader

I need a script that will crawl a list of websites and download all .jpg, .gif, .png files. I can think of some ways how to start like, fopen() or maybe curl(). And it downed on me I'd need to handle files writing over with the same name. And it would be cool to save the full URL to the file in a database with the path on the local server where I'm saving them. I was hoping someone might say, "Dude, that's simple, just do this..." before I spent hours guessing. Anyone? Thanks