Grayscale Image -> Alpha Transparency?

[pdxdev]

- I have a white logo on a black background. It has anti-aliased edges.

- I want to turn it into a white logo on a transparent background, where the anti-aliasing will be semi-transparent.

- This way, I can put my white logo on any background I want and have smooth edges that blend seamlessly into the background.

- (So, for example, the original 25% brightness at 100% opacity would become 100% brightness (white) at 25% opacity.)

- How do I do this?

[Medley]

Create a new (blank) layer.

Set the foreground color to white.

Go to the Channels pallette, and comand-click on the RGB (or Grey) channel. This creates exactly what you're looking for- a selection based on luminosity. white pixels are selected at 100%, black pixels are selected at 0%, and grey pixels are selected at some percentage relative to their brightness.

Switch back to the Layers Pallette, and highlight the new layer.

Go to Edit> Fill. In the dialog box that comes up, select 'use foreground color' from the drop-down menu. Click OK.

Done. Your new layer should now contain exactly what you want.

-Medley.