extract difference between two images

[c salman ahmed]

Hi,
I have a series of images with little change between them, I want to extract the difference between them for e.g. imagine 2 screenshots, one is the complete screenshot of an application, and the second one has the same screenshot but with the file drop down menu, i want only the difference between the 1st and the 2nd image (ie. the file drop down menu only). I want to automate this process. Is it possible via any photoshop action, or is there any other software that can do this. plz guide. thanks in advance

punk

[DrDoc]

What are you going to use it for?
If some form of animation, the program which layers and animates the slices does this automatically.

Otherwise, yeah, I know it's possible and even have software which can do it ... But I don't know of a way of doing this in Photoshop.