Comment 6 for bug 1579939

So this is my try at adding opacity to the mix.

As this should work for clones (which are probably a main target of the extension), I couldn't modify the single attributes, like stroke-opacity - they don't make a difference for clones (didn't know before I tried...).

So I resorted to modifying the whole object's opacity (in the style attribute). This has one disadvantage: opacity effects add up for grouped objects, as they are applied to the group, *and* to the objects within.

It still appears to be useful to me, and other color extensions also still seem to work with the modifications.
Please consider including this additional change, if it makes sense to you.

(also added jazzynico's __main__ thing)