Transparency to unpremultiplied RGB + Alpha
I have a transparent layer in Photoshop CS5 (so internally, it's most probably stored as unpremultiplied RGB component plus an alpha component per pixel).
Now I want to transform this to an opaque layer (just unpremultiplied RGB) + a alpha mask. the result should look the same as the original.
I can't just underlie the transparent layer with black, take the selection from it as a mask and merge the layers, because this would result in the alpha being premultiplied in the RGB values.
I hope you understand the problem and can give me a solution to it.
As an alternative explanation: I want the REVERSE process of this:
- create a new layer and paste in any image
- create a mask with a white-to-black gradient
- apply the layer mask
IMPORTANT: the layer is just for this example fully constant red - but you could think of any arbitrary image instead of the constant red. so - to go from state A to State B, one simply has to apply the layer mask.
I want to know how to go from State B to State A.