interpolated pcolor image

interpolation seems not to be supported for pcolor plots. Is that true? I want
to plot nonaequidistant gridded data, so imshow is not the right choice. Using
contourf with a large number of contour levels works fine but the eps output is
huge. I'd prefer to have the image embedded as bitmap in an eps, that's why I'd
like to use pcolor.
Regards, Christian