[R-SIG-Mac] poor quality png/tiff/pdf on mac

[M P]

Hello,
I cannot fix image quality e.g. generated with filled.contour(). Whether I
use tiff, png, jpeg, or pdf I always see vertical and horizontal lines at
every grid increment on the plots like the attached. There is no problem
when I plot in x11.
How to fix that?
Thanks,
Mark
[image: Inline image 1]
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