On Sat, Nov 1, 2008 at 2:06 AM, Renaud Aubin <aubin@nibua-r.org> wrote:
Thank Luigi for your response,  the problem is that the background color
rendering isn't the same if you comment out or not the following line :
draw fullcircle scaled 10cm shifted (0cm,0.25*\overlayheight) withcolor
transparent(1,0.5,white) withpen pencircle scaled 2cm;

After some experiments, the problem is solved ( hence not understood
???) using rgb=no in setupcolors...
They seem differents again 

It's maybe a viewer-centric problem : I use acroread 8.1.2 under linux.
no, I don't believe.
Try to investigate with \pdfcompresslevel0 at the beginning