Isn't our turbulence filter producing darker output than expected? The attached svg file is borrowed from the w3c test suite, and also contains the expected png output: our render looks draker.

I bumped into this trying to use turbulence as a displacement map: the displacement always globaly shifts the image downward and to the right. This is because the avarage value in each turbulence output channel is not 128 but much darker.

I think this is a bug... (maybe premuliplied alpha versus normal alpha color mode?)

Am I wrong?