[poppler] Text thinkess ?

[svchost at gmx.com]

Hi,
i'm new to poppler. Looking at some commercial pdf viewers (Xchange) i 
see that there is a setting (Gamma) that i can increase or decrease. 
This looks like its basically "font thickness".
I wish to increase this in poppler too, so that the text is more easy to 
read, does anyone know how may I do this? If this is a cairo thing any 
hint in the right direction is more than welcome.
I'm on win7 btw.

Thanks for any hints whatsoever !