Hi,
Jean-Christophe Dubacq <jean-christophe.dubacq@xxxxxxxxxxxx> writes:
> > In GIMP-1.3 this is as easy as deactivating all channels but alpha in
> > the channels dialog. All paint/fill operations will only affect the
> > alpha channel then.
>
> Well... I tried my version (1.3.19). Create a red picture. Create a
> new layer. Paint it black. And now, I would like to edit alpha directly
> with the pen tool ('pen'ing in black should in fact let red appear,
> since white is full opacity and black is transparent). But it doesn't
> work: whateve color is selected, the pen does not affect alpha.
The paintbrush can only increase opacity, if you need to decrease
opacity you will need to use the eraser. What you are describing
(black is transparent, white is opaque) only holds true for masks.
If you prefer to work that way, use a mask then.
Sven
