Comment 3 for bug 170565

You can classificate this issue as BUG!

http://blenderx.bl.funpic.de/inkscape/
download test svg+png files

You can see here some problems with this images (note that both rects have same 1px wide lines):
1) non rotated rectangle's rounded edges looks darker than 1px lines on the sides
2) rotated rectange looks darker than non rotated rectangle

to fix this: do a gamma-correction - theoreticaly this should be gamma 2.2 (=monitor) - but the result is not good - i tested with gamma 1.5 - and this was perfect

this test is only possible, because inkscape do "wrong linear" alpha calculation between black and white in example images...

to fix this "bug" - inkscape should do this:
1) convert colors to linear space (1/gamma = inverted gamma) - remember that you work in non-linear-space!!!
2) do alpha calculations
3) convert back to non linear space (gamma)

As you can see we need also a custom selectable gamma correction value

If you need more informations about this problem: read this great article - this describe that most graphic programs ignore gamma corrections and create wrong graphics...

http://www.4p8.com/eric.brasseur/gamma.html