[wp-hackers] Need some quick info about a wordpress core function

[R.J. Kaplan]

Hi,
I know this isn't really the place, but you're the guys who know  
WordPress best. Anyways, I'm writing a photo album plugin, and I'd  
like to make use of the thumbnail creation function built into  
wordpress. I spend hours looking through the code, but I can't find  
it. Can someone here please tell me where I can find it?
~Rubin