[SDL] A couple questions on SDL

[Lilith Calbridge]

I'm getting my feet wet with SDL and, in a great sense, video graphics
in general.  In looking for functions or combination of functions to do
what I need I've come across some things that it would help me to
understand better. 

First, what is YUV?  More explicitly what is the purpose of a YUV
overlay?  I've tried to find information through Google but pretty much
anything that discussed it did so from the view point that the reader
knew what it was.

Second, does SDL provide a function that I'm overlooking that will copy
the pixels of a small rectangle of a large surface into the pixels of a
smaller storage surface.  My purpose is to restore the background under
a blitted surface to it's original content before redrawing the object
at a displaced position.  I don't mind doing the coding myself but if
SDL supports this functionality it's probably more efficient than what
I'd come up with.

Thanks,
Lilith