Comment 21 for bug 381677

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Vladimir Savic (vladimir-firefly-savic) wrote :

I had to deal with this issue for many years. Here is what I think is the problem, but I still don't know whose bug is that...

Inkscape has to rasterize every svg effect.

1) Without added opacity, produced PDF looks like this: Image (rasterized svg effect). Period.
2) With opacity added on top of that effect (as is the situation with flag example), produced PDF looks like: Image (rasterized svg effect), one object group of that image clipped with PDF pattern (not to be confused with pattern you use in Inkscape and bitmap editing software).
That PDF pattern is just transparent image. Summary: Transparent image gets "clipped" with semi-transparent bitmap, which adds up. 50% transparency ends up clipped (think about it as masking in Inkscape terms) with another 50% transparency and you end up with 75% transparency.

I highly recommend trying Scribus layout application to test that. Install unstable 1.5.x to test much improved PDF import. After you import your PDF there, just ungroup until you are left without groups. Enjoy correct transparency.