And how this is different from wkhtmltoimage? http://code.google.com/p/wkhtmltopdf/
I'm not saying that the way I handle the rendering is any better than wkhtmltoimage's so feel free to use both and choose which you find it's better.
Also, run "make world" for Xorg some time and let me know if you still consider Xvfb lightweight. There's a reason the target is called "world" :)
And I will again point to you that lightweight is relative, if you know a better way to fake an X Server without xvfb just let me know and I'll use it on my tool.