how to make smooth curves with libgd 1.x?

I'm trying to use libgd 1.8.4 to draw circles. I got the circles going ok, but the edges are rough. pixelated. Is there anyway to smooth out the rough edges? my test. looks like with gd 2.0.1 this is made easier with truecolor images, which require 2.0.1. (I haven't tried it, but the docs imply that's one plus to 2.x.) is it possible with pre-2.x? Thanks.