Re: [Gimp-user] Invert alpha channel

[Eduard Braun <Eduard Braun2 gmx de>]

Am 12.07.2013 22:43, schrieb Mikael Ståldal:
> Is there an easy way in GIMP to invert the alpha channel of an image? 
> Transparent should be opaque, opaque should be transparent, almost 
> transparent should be almost opaque, etc.
Yes, there is:

1. Choose "Colors -> Components -> Decompose" from the menu and set
   "Color model" to "RGBA".
2. A new image is opened with all color channels (including alpha
   channel) decomposed as single layers.
3. Select the layer "alpha" and choose "Colors -> Invert" from the menu.
4. Choose "Colors -> Components -> Compose" from the menu, set "Color
   model" to "RGBA" and make sure the layers are correctly mapped to
   the channels (should be given if you did not reorder the layers)

Regards
Eduard