If a draw a shape on a bitmapped layer, I can fill it with a colour which is partially see through. This can be replaced with another colour that fully opaque.
But you can’t replace the fully opaque fill colour with a one with a lower Alpha Value, I.e. see through. Why?
If you fill it with a colour with a low Alpha Value, and then refill it again with the same colour, it has the effect of raising the Alpha Values. Again why?
Why when you draw a shape in a bitmapped layer, that you can fill it with a colour with a low Alpha Value, I.e. see through.
You can replace the fill with a more opaque colour, but this can’t be replaced with a fill with a lower Alpha Value? Why?
If you fill the shape with a fill, with a low Alpha Value, you can fill it again with the same colour, the effect is to increase the Alpha Value. Again Why?
By default the fill tool will fill on top of the previous color, multiplying it, that’s the way it works in the 0.6.6 release. If you try out the latest nightly build you’ll find that we’ve made a great deal of improvements to the bucket tool. Amongst those changes is the ability to change the blend mode, where “overlay” works the same way as in 0.6.6, then there’s a new “replace” mode, which will accomplish what you want, eg. replace with a lower alpha value and there’s “behind” which will fill behind the surface, eg. strokes.