[poppler] proposal: render dark text as black

[leidola at newcon.de]

Hello!

Printing some articles of online magazines using acrobat reader leads
to good-looking text on color laser printers whereas printing the same
PDF files using xpdf, gv or anything else yields poor text quality, as
the text is printed using colors(*).

Digging a bit further it seems as if acroread does something like using
a "luminescence threshold" below which the printed text is defined as
black, even if it is not gray, but something like

rgb 0.140993 0.121996 0.125002 

Is doing the same feasible? And if yes, where is the right way to put
it? Knowing where to start, I could try to create a patch.


(*): It looks as if there is a halo around the letters of the text;
it's not clear.

Thanks a lot,

Olaf