is true, both Skia and Cairo are quite large 2D Rendering Libraries. Qt is out due to licensing but it is just as large.
That pretty much leaves just AGG as Fog has been abandoned.
Can’t really see a reason not to go with AGG, Google has been using it all time for their Chrome PDF in part due to its excellent performance. AGG is also rasterizer used in generating maps in http://www.openstreetmap.org/.