Sorry for the inaccurate bug name, but I had no idea how to describe it.
If you render the attached page in cairo (full doc: http://www.dmi.unict.it/~cutello/introduzione.pdf), the background makes the text almost unreadable.
Created attachment 70041 [details]
Page 1 from the document
Created attachment 70042 [details]
Cairo rendering (wrong)
Created attachment 70043 [details]
Splash rendering (correct)