Anti-aliasing / smoothing

[luigifab]

Here are an example of the current result:

It is possible to create beautiful lines like this ones?

[raalkml]

Probably. The library I'm using, libgd, seems to support anti-aliased lines. It's not all there is to it: one still have to figure out how to connect the ends of lines and have them anti-aliased as well (round ends?).
Any suggestions welcome!

[raalkml]

This turned out not easy at all. The extremely simplistic code I currently use is absolutely not up to the task :-( as is libgd, which draws just horrible antialiased lines. Either I'm doing something very wrong, or its code is too, not really up to the task.
Currently considering using Cairo (a very powerful graphics library) or just bite the bullet and write the line rendering code myself.