sorry for my logged-out reply…
Well after some more discussion in our dev-team we may have an idea for a workaround.
Here it’s said, that “PD4ML ignores print CSS media type and respects only stylesheets defined for all, screen and proprietary pdf media types.”.
So, if we find out what is meant by “proprietary pdf media type”, we could redefine the css-classes that use the “filter:” property in the appropriate media-type *not* to use the “filter:” property, and pd4ml should ignore the property.

Edit: –> Wrong: @media pdf {} would give the semantical possibility to override stuff, but the parser goes through all css, of course…