Never heard the question asked...

Yeah, generally no one puts much thought into downsizing algorithms because they've been done again and again by so many industries (not just imaging, think video as well), and the logic is all the same - you're trying to take OUT details because you're removing pixels/detail.

You reduce something /5 and you have to figure out which 4 pixels are to be thrown out so you can only have 1 pixel left - what is the dominant color for it to be to "simulate" what detail is now gone - get it?

Yes - the big deal has always been UP-sizing since pixels need to be manufactured that were never there in the first place. How do you keep clean lines instead of simply bigger jaggies? How do you deal with the notion that the subtle colors were actually a cloth texture pattern? Stuff like that?

Just about ANY program will do the trick well when it comes down to down-sizing - any differences they may end up having will simply be so minimal no one would bother caring.

Hope this helps-

-Lew