[cairo] Apply / Composite smaller PNGs onto large background PNG?

[Jim Norton]

I'm somewhat new to GTK and very new to Cairo. I've been tasked to  
create an application that needs to take a PNG as a background and  
composite multiple PNG files that contains letters and numbers onto  
the background PNG so that I end up with a single PNG that can then be  
transformed, rotated, scaled etc. Any hints, tutorials, code samples  
that I might find useful? As is the case with GTK, the Cairo  
documentation appears somewhat lacking for a beginner trying to do  
something more complex than drawing shapes.

Thanks all.