layers difference

[justask]

Hello!

How can I create an automatic selection or alpha channel from two layers' difference?

I tried diffuse and difference blend modes, and manual selecting the "difference", but it was too complicated.
The layers are an animation file's frames.

thank you

[Tom]

Hi justask,

I'm not sure if i had the question well understood. But i will try two manners :

- The quickest i mean : copy merged

• menu Layers / Hide all layers
• switch as Visible the combined layers
• select the upper layer and menu Edit / Copy merged
• paste, you have a new layer, as a merged result, you can edit its alpha channel.

- not the faster but allows to combine 2 alpha channels :

• Edit the alpha channel of the both layers
• menu Adjust / Negative for one of them and copy
• paste on to the other alpha channel and set the blending mode
  in minimum or maximum, depending the result you wish

Tell us if that's you are waiting for

[justask]

Thank you for fast response.
But I think you misunderstood my question. It is my fault, my english is poor.
So I am trying to explain:
There are 2 image/layer. These images are frames from an animation/a movie. How can I detect the different part of the two frame/image/layer?
Just like a text file comparison, or a binary file comparison.
I need the selection(s) for the different part(s), or alpha mask (the not changed part is transparent, and the changed one is visible).
I hope my question is much clearer.

thank you

[Tom]

Hi,

Yes, the question is much clearer, but ...

Just like a text file comparison, or a binary file comparison.
it's a dreamed comparison, but it doesn't work like that in any image editing program i know.

I need the selection(s) for the different part(s), or alpha mask (the not changed part is transparent, and the changed one is visible).
That's exactly i have understood, but again ...
- an alpha mask returns only the solid, transparent, and relative transparent areas of a layer,
It doesn't return any information on a detail or another which are on a solid area between many other details.
- in a alpha mask, transparent areas of the layer are return as black color, solid as white, and relative transparent as relative grey colors.
- to apply the alpha mask on a layer you have to copy the alpha mask and select the layer : menu Layer / Transparency / Paste as Alpha channel

I don't know any manner to display only what has changed on the front of the layers, perhaps is it possible ??? but i don't believe,
on the other hand, the second way of my last post can return what has changed in Alpha channel (transparency) between two layers.

[justask]

OK, thank you very much for your answer.